docs: reconcile merged qualification and contributor checkpoints

[LIHUA919]

Goal and result

Reconcile the shared-authority frontier and contributor board with current merged and reviewed work. The old entries advertised another UTF-8 guard and migration design work, and treated the merged SQLite read-proof optimization as an open implementation PR.

Changes

• Update the bilingual RFC frontier for merged perf(authority): reuse owned state during SQLite and archive replay #4931 (9482a9496), retaining the earlier review context as history and all D2 budget/recovery/soak/promotion holds.
• Mark [Bug]: Windows non-UTF-8 locale — Path text I/O decodes structured state files with the locale encoding #4941 as native reporter verification/issue closeout after fix(usage-ping): pin UTF-8 on the state reads and guard the class #5160 supplied the package-wide guard; use the actual test paths.
• Route Legacy replan matcher treats 'installed' as a stall signal #4336 to its existing regression PRs test(quota): contract prose never triggers replan; advise stale runtimes #4397/test(quota): pin that prose summaries cannot trigger a replan #5162 and [Feature]: 统一默认本地状态路径为 .loopx，并提供从 .codex 的显式迁移 #4800 to approved Unify default local state under .loopx with explicit migration #4915 rather than duplicate implementation.
• Describe contributor-owned [Task]: Qualify SQLite D2 capacity and crash/replay recovery on the merged provider #4224's remaining evidence ledger after fix(sqlite): retain fast COUNT and add D2 qualification checks #4328/perf(authority): reuse owned state during SQLite and archive replay #4931 instead of advertising another generic crash/replay slice.

Validation and boundaries

• 36 contributor-board and RFC-index pytest cases pass on head 3d45c1b2e.
• examples/docs-governance-smoke.py passes; the changed three-file public-boundary check reports zero errors (two expected warnings for the deliberately absent isolated registry).
• git diff --check passes. Initial uv cache access was blocked; checks passed after using a disposable cache with the prepared checkout environment.
• GitHub metadata confirms perf(authority): reuse owned state during SQLite and archive replay #4931/fix(usage-ping): pin UTF-8 on the state reads and guard the class #5160 merged, Unify default local state under .loopx with explicit migration #4915 approved with no failed/pending checks, and test(quota): contract prose never triggers replan; advise stale runtimes #4397/test(quota): pin that prose summaries cannot trigger a replan #5162 still open. Existing docs: record local authority adoption and isolate rehearsal processes #5217 owns the adoption ledger; refactor(quota): resolve fallback advice from one typed snapshot #4061's separate RFC changes do not cover these status passages.
• Documentation only. D2 qualification and maintainer merge authority remain separate. The maintenance pass replaces stale current truth and distinguishes historical review state without adding another tracker or framework.