loc: replace reflection-based args with tuple-params + IDictionary overloads

[codemonkeychris]

Why

PR #353 skipped Localization_LocaleSwitching under AOT because
t.Message(key, new { name = "World" }) reflects over the anonymous type
to build the ICU args dictionary, and the trimmer drops the property
getters under NativeAOT (ctor + backing fields are statically reachable
from the new { ... } site, but property getters aren't, since the only
reader was a reflective GetProperties() call). GetProperties()
returned empty, MessageFormat.FormatMessage threw on {name}, the
catch swallowed, and the raw ICU pattern leaked through to the UI.

We don't want a reflection-based dispatcher in this code path anyway —
it forces every [UnconditionalSuppressMessage] we''ve written on the
type, and the security model (refuse arbitrary DTOs via
IsAcceptableArgsContainer) is doing nothing the type system couldn''t
do statically.

What

Replace the object?-typed args parameter with two AOT-safe overloads:

// 1. Explicit dict — for shared/programmatic args
public string Message(MessageKey key, IDictionary<string, object>? args = null);

// 2. Tuple-params — for the compact inline case
public string Message(MessageKey key,
    (string Name, object Value) arg1,
    params (string Name, object Value)[] more);

Callers go from this:

t.Message(Greeting, new { name = "World" })
t.Message(SearchResults, new { count = 0, query = "test" })

to this:

t.Message(Greeting, ("name", "World"))
t.Message(SearchResults, ("count", 0), ("query", "test"))

Same shape for RichMessage. The tagged variant uses the dict overload
because params must be last:

t.RichMessage(Loc.Profile.Welcome,
    args: new Dictionary<string, object> { ["name"] = "Alice" },
    tags: new() { ["bold"] = text => Text(text).Bold() })

ValueTuple is a nominal type with concrete fields — building a
Dictionary<string,object> from tuple values needs zero reflection,
so the whole IL2026/IL2070 surface for this method disappears.

Deleted

• ToArgsDictionary, IsAcceptableArgsContainer, _propertyCache
• The [UnconditionalSuppressMessage("Trimming", "IL2026"/"IL2070")] attrs
• using System.Reflection, System.Collections.Concurrent,
  System.Diagnostics.CodeAnalysis (now unused)
• The [LocArgs] soft opt-in marker (string-name match in
  IsAcceptableArgsContainer)

Migrated callers

• Selftest + AppTests localization fixtures (two files)
• IntlAccessorTests, RichMessageTests
• Reactor.Cli/Loc/SourceRewriter: emits tuple syntax now. CLI codegen
  for interpolated strings now writes t.Message(key, ("name", expr))
  instead of t.Message(key, new { name = expr }). Updated
  SourceRewriterTests assertions.
• Docs: _pipeline/templates/localization.md.dt narrative and
  _pipeline/apps/localization/App.cs snippets (the compiled
  docs/guide/localization.md regenerates from these). Plus the
  hand-edited docs/reference/localization-howto.md example.

AOT skip list

• Localization_LocaleSwitching removed from DefaultAotSkipPatterns
  in SelfTestRunner.cs.
• "Localization with anonymous-type args" row removed from
  docs/aot-support.md — there''s no anonymous-type path left to break.

Verified

• dotnet build src/Reactor — clean (AOT warnings remain as errors).
• dotnet test tests/Reactor.Tests --filter "FullyQualifiedName~Localization" — 282/282 pass.
• dotnet run --project tests/Reactor.AppTests.Host -- --self-test
  (JIT, full suite) — 0 failures.
• AOT republish + selftest pending verification on this PR; will report
  back with numbers.

Breaking change

t.Message(key, new { name = "..." }) no longer compiles. The compiler
error is reasonably clear ("cannot convert anonymous type to
IDictionary<string, object>"); no analyzer needed. Migration is a
mechanical new { name = X } → ("name", X).

Base

This PR is based on codemonkeychris/aot-selftest-skips-round3
(PR #353). When that merges, GitHub will retarget this PR to main.

[codemonkeychris]

AOT verification complete.

Full AOT selftest run against the published binary on this branch:

Metric	Before (PR #353)	After this PR
ok sub-assertions	2184	2224
not ok	0	0
# SKIP	193	192
Localization_LocaleSwitching	skipped	runs, 40/40 pass

The 40 newly-passing sub-assertions cover Greeting / Plural_Zero / Plural_Five / Search_Zero / Search_One / Search_Many / Direction across en-US, ko-KR, ar-SA, ja-JP, de-DE, plus en-US round-trip. Tuple-params overload behaves identically under AOT and JIT.

Pushed CONTRIBUTING.md count refresh to match (192 skipped, ~543 passed, 0 failed).

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

This PR removes reflection-based localization argument handling (which breaks under NativeAOT trimming) and replaces it with AOT-safe argument passing via IDictionary<string, object> and tuple-params overloads for Message/RichMessage.

Changes:

• Updated IntlAccessor to accept explicit dictionaries and added tuple-params overloads that build args without reflection.
• Migrated call sites (tests, fixtures, CLI source rewriter) from anonymous objects to tuple args / dictionaries.
• Updated documentation and AOT skip list to reflect the new, AOT-safe localization args model.

Show a summary per file

File	Description
tests/Reactor.Tests/Localization/SourceRewriterTests.cs	Updates assertions to match tuple-arg codegen output.
tests/Reactor.Tests/Localization/RichMessageTests.cs	Switches rich-message args to explicit dictionary.
tests/Reactor.Tests/Localization/IntlAccessorTests.cs	Migrates tests from anonymous args objects to tuple args.
tests/Reactor.AppTests.Host/SelfTest/SelfTestRunner.cs	Removes localization fixture from AOT skip list and updates rationale.
tests/Reactor.AppTests.Host/SelfTest/Fixtures/LocalizationFixtures.cs	Migrates localization fixture calls to tuple args.
tests/Reactor.AppTests.Host/Fixtures/LocalizationFixtures.cs	Migrates app-test fixture calls to tuple args.
src/Reactor/Core/Localization/IntlAccessor.cs	Core API change: dictionary-based args + tuple overloads; removes reflection helpers.
src/Reactor.Cli/Loc/SourceRewriter.cs	Emits tuple-arg syntax instead of anonymous objects.
docs/reference/localization-howto.md	Updates example to use tuple args.
docs/aot-support.md	Removes anonymous-type localization args as an AOT limitation.
docs/_pipeline/templates/localization.md.dt	Updates narrative to describe tuple args as the primary interpolation shape.
docs/_pipeline/apps/localization/App.cs	Updates code snippets to use tuple args.
CONTRIBUTING.md	Updates expected AOT skip/pass counts after removing the localization skip.

Copilot's findings

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• Files reviewed: 13/13 changed files
• Comments generated: 5

[codemonkeychris]

Addressed all 5 reviewer findings in 615b10f:

1. BuildArgs null semantics — switched the tuple value type to object?, drop null-valued tuples before they hit the dict (matches the removed ToArgsDictionary''s skip-nulls behavior), added an IntlAccessorTests case pinning it.
2. cref XML warnings on RichMessage doc — the cref referenced a signature with C# keyword generics + nullability, which doesn''t resolve. Replaced with a prose reference + <c>RichMessage</c>.
3. SourceRewriter ICU param-name escaping (two comments, same finding) — now uses SymbolDisplay.FormatLiteral(param, quote: true) to produce a valid C# string literal so a placeholder with \" or \\ can''t corrupt the emitted source.
4. Template phrasing — tightened (name, value) to (\"name\", value) with an explicit sentence that the first item is the placeholder name as a string literal. Regenerated docs/guide/localization.md from the template.

JIT localization tests: 283/283 (the +1 is the new null-skip case).