fix(validator): close four validator gaps from adopter housekeeping (closes #215)

[montfort]

Closes #215.

Adopter feedback from the Sentinel 150-doc housekeeping pass (PR #110). All four gaps were verified unaddressed against the current code before implementing.

Changes

Gap	Class	Fix
1 — OBS-001	False positives (19/19)	Widen the observability content check to a broad, case-insensitive vocabulary (otel, metric/métrica, span, trace, dashboard, collector, alert, slog, histogram, telemetr, …). The rule only fires on docs already tagged observabilidad/observability, so the tag is the real signal.
2 — dual-origin	Schema vs guidance (N=5)	Bless canonical execution_ailogs (close-time aggregation for a spec-originated Charter) + context_spec (area context for an AILOG-originated one), keeping originating_* mutually exclusive. Wired into the architecture implemented overlay + KG edges; CHARTER-AILOG-REF/SPEC-REF cover the new fields.
3 — CHARTER-FILES-EXIST	Historical-record noise (16/19)	Add (external) / (removed) / (relocated: <path>) exemption markers alongside (new). Unmarked missing paths (e.g. unsubstituted AILOG-YYYY-MM-NNN placeholders — the 3 real bugs in the report) are still flagged.
4 — META-003	Authoring UX (28/93)	Suggest the nearest canonical status — semantic alias map (done/completed/closed → accepted, …) + Levenshtein fallback for typos — and enumerate the lifecycle vocabulary inline in the AILOG template.

Design notes

• Severity has only Error/Warning (no Info), and a closed Charter's table is the place the placeholder bugs live — so Gap 3 uses explicit markers rather than the issue's alternative "downgrade to info on closed", which would have sacrificed that detection.
• Gap 2 keeps the schema's not:{required:[originating_ailogs, originating_spec]} exactly-one rule; the new fields are not subject to it.

Scope

• core: charter.rs (struct), architecture/gather.rs, entities.rs, charter_files.rs (FileExemption).
• CLI: validation.rs (Gaps 1, 2-refs, 3, 4), charter_schema.rs tests.
• Framework: charter.schema.v0.json, charter + AILOG templates (EN/es/zh-CN), straymark-charter-new skill (4 variants, codex regenerated).
• No version bumps or tags — release prepared separately (touches core + CLI + framework).

Verification

• cargo test — full workspace green (348 lib + integration; new unit/integration tests per gap).
• cargo build --release — clean. cargo clippy — no new warnings in touched files.
• gen_codex_skills --check — in sync (15 skills).
• Dogfood on a temp project: status: done → Did you mean 'accepted'?; charter originating_spec + execution_ailogs → no mutual-exclusion error; (external)/(removed) paths not flagged while an unmarked missing path still is; AILOG tagged observability with OTel/dashboard → no OBS-001.

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