Pure read/write/lookup for the vault sidecar index that will hold page identity
(pageId) + collision token (slugId) keyed by file path, so the .md files can be
clean markdown. parseVaultIndex is tolerant (missing/garbage/bad entries degrade
to empty/skipped — never crashes a cycle); serializeVaultIndex is deterministic
(sorted keys -> stable diffs, no churn). Lookups (pageIdAt, pathForPageId reverse,
trackedPageIds) + mutations (set/remove/move). NOT wired into pull/push yet — no
behavior change. 5 unit tests; engine suite green.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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