fix: harden Happy session flows and self-hosting

[Scoteezy]

Summary

Hardens Rig session creation, daemon ownership, self-hosted runtime configuration, persistence, and session UI flows.

• Preserve selected worktrees while rejecting unsafe worktree names.
• Keep Rig retries idempotent across pending responses, path normalization, and worktree naming changes.
• Prevent stale daemon state from force-killing an unverified reused PID.
• Keep session heartbeat suppression ownership-safe and reactivate restarted sessions.
• Load self-hosted web runtime configuration safely under CSP and validate server URLs.
• Correct project grouping, worktree labels, accessibility, Android text selection, and conversation text scaling.
• Add configurable daemon idle and concurrency limits and reap detached, orphaned, and closed tmux session trees.
• Isolate Claude startup from repository-controlled settings, hooks, and ambient MCP discovery.
• Persist daemon resume state and fall back to provider-level resume when a Happy session is no longer locally tracked.

Validation

• pnpm --filter happy-app typecheck
• pnpm --filter happy-app test (954 tests)
• pnpm --filter happy test (807 tests)
• pnpm --filter happy-server typecheck
• pnpm --filter happy-server typecheck:prod
• pnpm --filter happy-server test (108 tests)
• Session lifecycle targeted CLI tests (141 tests)
• Resume fallback targeted app tests (9 tests)
• pnpm --dir packages/happy-cli typecheck
• git diff --check

Issues

Closes #1687.
Closes #1688.
Closes #1693.
Closes #1694.

Relates to #1677, #1657, #1654, #1652, and #1651.