Prevent concurrent servers from sharing a data directory

[ymichael]

What was wrong

The server had no data-directory singleton lock. During overlapping dev restarts, a second server could open the same SQLite database before losing its port bind. Because in-flight provisioning context is process-local, startup recovery in that second process could treat a live starting thread as orphaned and emit a false thread_provisioning_failed event.

What changed

• Extracted the host daemon robust lock implementation into a shared @bb/process-utils data-directory lock module, including stale-lock recovery and compromise handling.
• Added a server.lock acquired before logger creation, initDb(), and startup recovery.
• Let a recently crashed owner's lock age through the stale window during startup while still rejecting a lock refreshed by a live server before SQLite opens.
• Made compromise re-acquisition timers non-owning so releasing the lock cannot pin a shutting-down process.
• Kept synchronous exit cleanup armed until asynchronous unlock finishes.
• Held server ownership until shutdown, with cleanup on both normal shutdown and startup failure.
• Kept the host daemon on the same shared implementation through its existing wrapper without forwarding ignored options.
• Wire changes: none. HOST_DAEMON_PROTOCOL_VERSION is unchanged.

How you verified

• Added regressions for rejecting a live server before initDb(), reclaiming a fresh orphaned server lock, releasing ownership after startup failure, releasing during compromise re-acquisition, and retaining exit cleanup through asynchronous unlock.
• Added shared lock tests for compromise re-acquisition, stale-lock recovery, and yielding to a live contender, plus host-daemon wrapper coverage.
• pnpm exec turbo run test --filter=@bb/server --force — 2,037 tests passed.
• pnpm exec turbo run test --filter=@bb/host-daemon --force — 557 tests passed.
• pnpm exec turbo run test --filter=@bb/process-utils --force — 25 tests passed.
• pnpm exec turbo run typecheck --filter=@bb/process-utils --filter=@bb/server --filter=@bb/host-daemon passed.
• pnpm exec turbo run build --filter=@bb/server --filter=@bb/host-daemon passed.
• node packages/plugin-sdk/scripts/check-npm-version-guard.mjs passed.

Related to #2190: prevents concurrent bb server access to the database directory, but does not resolve the WAL durability/reversion issue.

Fixes: no linked issue.

AGENT GENERATED