feat(storage): activate exact v8 runtime

[ebarti]

Summary

• make exact schema v8 the only Python and TypeScript runtime contract
• migrate exact v6 and v7 databases to v8 through the stopped-runtime candidate, paired-backup, atomic-install, and rollback protocol
• make the v6-to-v8 intermediate journal-bound so crash recovery removes every candidate artifact
• enforce SQLite foreign keys on runtime connections and preserve tenant ownership when discovery events are recorded
• advance the public release-version contract from exact schema v7 to exact schema v8
• document exact-v8 update, storage, recovery, and QA behavior

Stack

• depends on feat(storage): add exact v8 benchmark schema #790, which adds the frozen exact-v8 compensation benchmark schema
• fix(compensation): parse posted ranges from descriptions #789 remains the bottom stack layer for employer-posted salary extraction and display

Validation

• corepack pnpm python:lint — passed
• corepack pnpm python:test — 3504 passed, 2 skipped
• formerly failing foreign-key and tenant slice — 95 passed
• focused Python migration/runtime suite — 53 passed
• corepack pnpm api:check — passed
• API test suite — 771 passed
• real Python/Node-backed native v6-to-v8 migration integration under go test -race — passed
• launcher race suite excluding the fixed-port hermetic lifecycle test — passed; that single aggregate test is environment-constrained because the active local Temporal service owns port 7233
• node --test --test-name-pattern='public application versions agree' scripts/version-contract.test.mjs — passed against the rebased v8 candidate
• corepack pnpm docs:build — passed
• git diff --check — passed
• independent Tier-3 review — Gate PASS, 0 Blocker / 0 High / 0 Medium / 0 Low

Checklist

• I ran the relevant local checks and listed them above.
• I did not include secrets, private profile data, resumes, generated application materials, raw logs, browser profiles, SQLite databases, or local paths.