feat: add the local fleet IDE

[gnanirahulnutakki]

Summary

• ship sith ui as a build-free frontend embedded in the existing single Go binary
• render the same cache, Tier-1 lenses, ordering, coverage, search/correlation, and exact-context local operations as CLI/TUI
• enforce loopback-only bind, exact Host/Origin, per-process capability, restrictive CSP, bounded refresh/forward resources, and preview-bound YAML apply
• require explicit disclosure before Secret data enters edit mode

Verification

• make ci — format, vet, golangci-lint, govulncheck, race+coverage, warm-cache p95, tagged subprocess E2E, and build all pass
• make e2e-kind — digest-pinned two-cluster gate passes under -race in 73.798s, including one unreachable context
• Playwright desktop and 390px flows cover search, correlation, inspector, YAML, logs, preview/apply, and port-forward lifecycle with zero console errors/warnings
• GitHub Dependabot, CodeQL, and secret-scanning queues: 0 open alerts

Security review

• local red-team review covered every changed handler, browser sink, capability boundary, and session owner
• fixed overlapping hydration amplification, unbounded forward sessions, implicit Secret disclosure, and detached background context ownership
• CodeRabbit CLI was unavailable; Codex Security's MCP App could not render because the client requested missing UI resource 0.1.55 while the server advertised 0.1.63. Neither was represented as a passing review.

Operator/cost notes

• no account, telemetry, external asset, cloud resource, or persistent cache is introduced
• browser polling reads the in-memory cache; explicit refreshes are single-flight
• active web-owned port-forwards are capped at 16 and closed with the application

Closes #34