log: review fixes — AsyncAppend ziggy rewrite, bug fixes

AsyncAppend (full rewrite):
- Non-generic struct with allocator-based pre-allocation (zero hot-path alloc)
- Cache-line aligned cursors (128B) to prevent false sharing
- Epoch-based condvar parking replaces spin+sleep consumer loop
- Wrapping arithmetic (+%) throughout for long-running correctness
- Better memory orderings (monotonic for cursors, release/acquire for sequences)
- @bitcast diff calculation replaces @intcast overflow risk

Bug fixes from adversarial review:
- EnvFilter.fromEnv(): use std.posix.getenv (process-lifetime pointer)
  instead of getEnvVarOwned into stack buffer (was use-after-free)
- Dispatcher.emit(): save/restore diag_attrs.len across fan-out dispatches
  (diagnostic enrichment was contaminating subsequent dispatches)
- JsonLayout: escape all control chars U+0000-U+001F per RFC 8259 §7
- LogfmtLayout: escape \r and \t (needsQuoting detected them but
  writeLogfmtEscaped didn't handle them)

Prior auto-fixes included:
- Record.zig: AttrIterator.next() rewritten from recursion to while loop
- comptime_checks.zig: doc strings fixed *Self → *const Self
- root.zig: global dispatcher redesigned with single atomic pointer swap

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: grapebaba

.claude/worktrees/fix+atomic-ordering

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+Subproject commit 6860e0e04b866ad6797299fc268a03202ec27246

.github/agents/forkchoice-test-comparator.agent.md

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+/Users/grapebaba/.claude/plugins/cache/claude-plugins-official/remember/0.1.0/scripts/save-session.sh: line 135: cd: /Users/grapebaba/.claude/plugins/cache/claude-plugins-official/.claude/remember: No such file or directory
+/Users/grapebaba/.claude/plugins/cache/claude-plugins-official/remember/0.1.0/scripts/save-session.sh: line 140: [: : integer expression expected
+/Users/grapebaba/.claude/plugins/cache/claude-plugins-official/remember/0.1.0/scripts/save-session.sh: line 142: [: : integer expression expected
+/Users/grapebaba/.claude/plugins/cache/claude-plugins-official/remember/0.1.0/scripts/save-session.sh: line 164: cd: /Users/grapebaba/.claude/plugins/cache/claude-plugins-official/.claude/remember: No such file or directory