fix(muxer): 使用 BCP 47 语言标签并禁用 IETF 规范化

mkvmerge 没有独立的 --language-ietf 输入选项，因此字幕轨道原先的
"--language-ietf 0:<ietf_language>" 写法无效。改为通过 --language 直接
传入 IETF BCP 47 标签（mkvmerge 会自动写入 LanguageIETF 与兼容的 legacy
Language 元素）。同时在命令开头加入全局参数 --normalize-language-ietf off，
防止 mkvmerge 重写我们显式设置的语言标签。

fix(snapshot): 信任由已校验归档预览出的字幕字体路径

归档预览会在字体文件实际存在之前，把未来的提取路径写入计划，因此这些
路径不会出现在 snapshot.files 中。validate_plan_snapshot 现在会从
digest 已校验的字体归档重新计算出预览出的字体路径集合，并据此放行；
在 subset 模式下这一点尤其重要，因为规划期的回退逻辑可能保留全部预览
字体。真正不在归档预览中、也无法被追踪的字体路径仍会被拒绝（Untrusted
attachment path），避免放宽校验带来的安全隐患。

test: 补充 muxer 与 snapshot 相关用例

- test_muxer_extended: 新增用例断言 --language-ietf 不再出现，且 --language
  使用 BCP 47 标签；导入 SubtitleTrackPlan。
- test_snapshot: 新增两个 subset 模式用例，分别验证由已追踪归档预览出的
  字体路径被接受，以及未在归档预览中的未信任字体路径被拒绝。

Author: Masterain98

plexmuxy/muxer.py

@@ -129,6 +129,9 @@ def runtime_failure(
 
 def build_mkvmerge_command(plan: MuxPlan, output_path: Path, mkvmerge_path: str) -> list[str]:
     command = [mkvmerge_path, "--output", str(output_path)]
+    # Keep mkvmerge from rewriting our explicit IETF language tags.
+    command.append("--normalize-language-ietf")
+    command.append("off")
     source_audio = [track for track in plan.source_tracks if track.type == "audio"]
     included_audio_ids = [track.id for track in source_audio if track.included]
     if source_audio and not included_audio_ids:
@@ -151,8 +154,10 @@ def build_mkvmerge_command(plan: MuxPlan, output_path: Path, mkvmerge_path: str)
             track = subtitle_by_path[path]
             command.extend([
                 "--track-name", f"0:{track.track_name}",
-                "--language", f"0:{track.mkv_language}",
-                "--language-ietf", f"0:{track.ietf_language}",
+                # mkvmerge's --language option accepts IETF BCP 47 tags and
+                # writes both LanguageIETF and the compatible legacy Language
+                # element. There is no separate --language-ietf input option.
+                "--language", f"0:{track.ietf_language}",
                 "--default-track-flag", f"0:{'yes' if track.default_track else 'no'}",
                 "--forced-display-flag", f"0:{'yes' if track.forced_track else 'no'}",
                 str(track.path),

plexmuxy/snapshot.py

@@ -161,6 +161,44 @@ def validate_plan_snapshot(snapshot: MuxPlanSnapshot, config: AppConfig) -> None
     existed = {path.resolve() for path in snapshot.outputs_existing}
     from .planner import build_output_path
 
+    # Archive previews deliberately put future extraction paths in a plan before
+    # those font files exist, so they cannot be present in ``snapshot.files``.
+    # Recompute the paths from the digest-validated archives instead of broadly
+    # trusting every untracked path below Fonts. This is especially important in
+    # subset mode, where a planning-time fallback may retain all previewed fonts.
+    previewed_archive_fonts: set[Path] = set()
+    fonts_root = (snapshot.input_dir / "Fonts").resolve()
+    archive_extensions = set(config.media.font_archive_extensions)
+    untracked_attachments = {
+        attachment.path.resolve()
+        for plan in snapshot.plans
+        for attachment in plan.attachments
+        if attachment.path.resolve() not in tracked
+    }
+    archive_snapshots = [
+        item
+        for item in snapshot.files
+        if item.path.suffix.casefold() in archive_extensions
+    ]
+    if untracked_attachments and archive_snapshots:
+        from .font import preview_font_archive
+
+        for archive_snapshot in archive_snapshots:
+            try:
+                previewed_archive_fonts.update(
+                    path.resolve()
+                    for path in preview_font_archive(
+                        archive_snapshot.path,
+                        fonts_root,
+                        config.media,
+                        config.font,
+                    )
+                )
+            except Exception as exc:  # noqa: BLE001 - archive readers expose library-specific errors.
+                raise StalePlanError(
+                    f"Planned font archive can no longer be inspected: {archive_snapshot.path}: {exc}"
+                ) from exc
+
     for plan in snapshot.plans:
         output = plan.output_path.resolve()
         if plan.source_video.resolve() not in tracked:
@@ -184,13 +222,14 @@ def validate_plan_snapshot(snapshot: MuxPlanSnapshot, config: AppConfig) -> None
         expected_output = build_output_path(plan.source_video, snapshot.input_dir, config).resolve()
         if output != expected_output:
             raise StalePlanError(f"Plan output does not match the saved configuration: {output}")
-        fonts_root = (snapshot.input_dir / "Fonts").resolve()
         for attachment in plan.attachments:
             attachment_path = attachment.path.resolve()
             if attachment_path in tracked:
                 attachment_snapshot = tracked_snapshots[attachment_path]
                 if snapshot.schema_version >= 2 and attachment_snapshot.sha256 is None:
                     raise StalePlanError(f"Planned attachment has no digest: {attachment.path}")
+            elif attachment_path in previewed_archive_fonts:
+                continue
             elif font_mode == "subset" or fonts_root not in attachment_path.parents:
                 raise StalePlanError(f"Untrusted attachment path in plan: {attachment.path}")
         intent = plan.font_subset_intent

tests/test_muxer_extended.py

@@ -2,7 +2,14 @@
 from types import SimpleNamespace
 
 from plexmuxy.config import default_config
-from plexmuxy.models import AttachmentPlan, AudioTrackPlan, MuxPlan, SourceTrackInfo, VerificationResult
+from plexmuxy.models import (
+    AttachmentPlan,
+    AudioTrackPlan,
+    MuxPlan,
+    SourceTrackInfo,
+    SubtitleTrackPlan,
+    VerificationResult,
+)
 from plexmuxy.muxer import build_mkvmerge_command, execute_mux_plan, inspect_source_tracks, verify_mux_output
 
 
@@ -79,6 +86,30 @@ def test_mkvmerge_command_uses_no_audio_only_for_source_input(tmp_path):
     assert command[-1] == str(external)
 
 
+def test_mkvmerge_command_sets_subtitle_bcp47_language_with_supported_option(tmp_path):
+    subtitle = tmp_path / "Example.JPSC.ass"
+    plan = MuxPlan(
+        tmp_path / "source.mkv",
+        tmp_path / "output.mkv",
+        subtitle_tracks=[SubtitleTrackPlan(
+            subtitle,
+            "jp_sc Studio",
+            "chi",
+            "zh-Hans",
+            True,
+            False,
+            "exact",
+        )],
+    )
+
+    command = build_mkvmerge_command(plan, plan.output_path, "mkvmerge")
+
+    assert "--language-ietf" not in command
+    language_index = command.index("--language")
+    assert command[language_index + 1] == "0:zh-Hans"
+    assert command[-1] == str(subtitle)
+
+
 def test_execute_mux_plan_success_uses_verified_temp_then_replaces(monkeypatch, tmp_path):
     source = tmp_path / "source.mkv"
     source.write_bytes(b"source")

tests/test_snapshot.py

@@ -1,12 +1,14 @@
 import hashlib
 import json
 import os
+import zipfile
 
 import pytest
 
 from plexmuxy.config import config_to_dict, default_config, parse_config
 from plexmuxy.errors import StalePlanError
 from plexmuxy.models import (
+    AttachmentPlan,
     FileSnapshot,
     FontFaceRef,
     FontSubsetGroupIntent,
@@ -219,6 +221,48 @@ def test_schema3_tracks_archive_not_future_extraction_path(tmp_path):
         validate_plan_snapshot(snapshot, config)
 
 
+def test_subset_snapshot_accepts_future_attachment_previewed_from_tracked_archive(tmp_path):
+    video = tmp_path / "Example.mkv"
+    archive = tmp_path / "Fonts.zip"
+    future_font = tmp_path / "Fonts" / "Demo.otf"
+    video.write_bytes(b"video")
+    with zipfile.ZipFile(archive, "w") as bundle:
+        bundle.writestr("Demo.otf", b"font payload")
+    config = default_config()
+    config.font.mode = "subset"
+    plan = MuxPlan(
+        video,
+        tmp_path / "Example_Plex.mkv",
+        attachments=[AttachmentPlan(future_font)],
+        font_subset_intent=FontSubsetIntent(1, 1, (), ()),
+    )
+    snapshot = create_plan_snapshot(tmp_path, [plan], config, extra_inputs=[archive])
+
+    assert future_font.resolve() not in {item.path for item in snapshot.files}
+    validate_plan_snapshot(snapshot, config)
+
+
+def test_subset_snapshot_rejects_untracked_font_not_in_archive_preview(tmp_path):
+    video = tmp_path / "Example.mkv"
+    archive = tmp_path / "Fonts.zip"
+    untrusted_font = tmp_path / "Fonts" / "Injected.otf"
+    video.write_bytes(b"video")
+    with zipfile.ZipFile(archive, "w") as bundle:
+        bundle.writestr("Demo.otf", b"font payload")
+    config = default_config()
+    config.font.mode = "subset"
+    plan = MuxPlan(
+        video,
+        tmp_path / "Example_Plex.mkv",
+        attachments=[AttachmentPlan(untrusted_font)],
+        font_subset_intent=FontSubsetIntent(1, 1, (), ()),
+    )
+    snapshot = create_plan_snapshot(tmp_path, [plan], config, extra_inputs=[archive])
+
+    with pytest.raises(StalePlanError, match="Untrusted attachment path"):
+        validate_plan_snapshot(snapshot, config)
+
+
 def test_schema1_v2_config_remains_valid_outside_subset_mode(tmp_path):
     video = tmp_path / "Example.mkv"
     video.write_bytes(b"video")