fix(mcp): make i18n:false delete and meta cleanup safe

[ABB65]

What & why

Two bugs a project hit while cleaning up an i18n: false collection (reported against @contentrain/[email protected]), plus a source-hygiene fix found along the way.

Base branch note: this was originally cut from fix/field-constraints, but that branch has since merged (PR #84) and 2.0.0 released from main, so it now targets main directly. The commit rebases cleanly — the diff is exactly the 13 files below.

Issue 1 — content_delete(locale=<non-default>) on i18n: false was destructive

On a non-i18n model, content is locale-agnostic (data.json) with a single meta record pinned to the default locale. Passing a non-default locale silently mapped onto data.json and the default-locale meta, so the call:

• emptied the shared data.json (deleted the real, published entry),
• deleted the default-locale meta (e.g. tr.json),
• left the meta for the locale actually named (e.g. en.json) untouched,

and reported a files_removed path (.../en.json#<id>) that never existed — the opposite of the request.

Fix: planContentDelete (and the legacy deleteContent) now reject a locale-scoped delete on an i18n: false model with a clear error. Omit locale to delete the entry.

Issue 2 — validate fix:true would not remove the stray meta it warns about

The "Meta layout mismatch" warning had no remediation path, so fixed stayed 0. checkStrayNonI18nMeta now consolidates deterministically and never decides a status:

• default-locale meta present → the strays are redundant, so prune them (the published record stays authoritative — no status is merged or downgraded);
• default-locale meta absent, one stray → migrate it to the default path so the record is preserved;
• several strays, no default → ambiguous, so leave the warning for the author to resolve.

Subtle interaction handled: the orphan-content pass fabricates a draft default-locale meta for content lacking meta at the default locale. Consolidation now runs before that pass and gates its fabrication while a stray is unresolved — otherwise a lone published stray would be shadowed by a fabricated draft and then deleted on a later run. The remediation is idempotent.

Issue 3 (found while investigating) — raw NUL bytes in validator/project.ts

The document validator used two literal NUL bytes as a Map-key separator, which made file/grep/diff classify the source as binary (and silently broke the first grep of this investigation). Replaced with a unicode escape — identical at runtime, plain-text source.

Tests & gates

• New: planContentDelete guard (non-i18n reject / i18n allow / locale-free allow), legacy deleteContent guard, disk-backed validate fix:true stray-meta cases (prune, migrate, ambiguous no-op, idempotency).
• tsc --noEmit: 0 errors · oxlint on all changed files: 0 warnings.
• Targeted + validator suites pass; contentrain_content_delete tool test passes in isolation (17/17).
• The full git-heavy suite was not run to green here — those files (branch-lifecycle, bulk, identity, …) time out under load from serial-git slowness, unrelated to this change (bulk delete_entries passes no locale, so the guard never fires).

Docs, rules, and skills updated (docs/packages/mcp.md, rules/shared/mcp-usage.md, contentrain-validate-fix skill + workflow, mcp-tools.md, tool description string).

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