Harden storage recovery and index readiness

[ajroetker]

Summary

• make exact restore retries finish durable runtime repair through the authoritative cached writer under exclusive structural admission, preventing successful-but-unreadable restores
• fence full-text publication planning against same-name index replacement and precompute bounded publication chunks once, avoiding stale catalog access and repeated whole-suffix projection work
• return a documented JSON table_storage_unreadable response for non-retryable table read failures, including InvalidManifest and corrupt compressed blocks
• treat managed-embedding missing-field outcomes as terminal skips for readiness and progress while retaining strict coverage diagnostics
• regenerate OpenAPI and all checked-in clients

Fixes #441
Fixes #442

Validation

• make generate
• env ZIG_GLOBAL_CACHE_DIR=/tmp/antfly-zig-generated-global make zig-generated-check
• zig build api-public-table-http-docid-test -Doptimize=Debug (21 passed)
• zig build lib-api-derived-coverage-test -Doptimize=Debug (35 passed)
• zig build api-table-writes-production-regression-test -Doptimize=Debug (67 passed)
• zig build index-manager-test -Doptimize=Debug (1554 passed, 2 skipped)
• zig build db-test -Doptimize=Debug (3106 passed, 7 skipped)

The long CI matrix is left to GitHub Actions.