feat(cli): add logs command for gateway log access (#1105)

- Add `ironclaw logs` to tail gateway.log with reverse-seek (O(output) memory, no full-file load)
  - Add `--follow` for live SSE streaming from /api/logs/events
  - Add `--level` to get/set runtime log level via /api/logs/level
  - Support --json, --plain, --local-time, --url, --token, --timeout flags
  - Respect --config for gateway address/token resolution (consistent with other CLI commands)
  - Fail explicitly when --config points to invalid file instead of silent fallback
  - Wire Logs variant into Command enum and main.rs dispatch
  - Add 9 unit tests (tail_file chunked read, colorize, timestamp conversion, JSON output)
  - Update FEATURE_PARITY.md: logs ❌ → 🚧

FEATURE_PARITY.md

@@ -176,7 +176,7 @@ This document tracks feature parity between IronClaw (Rust implementation) and O
 | `browser` | ✅ | ❌ | P3 | Browser automation |
 | `sandbox` | ✅ | ✅ | - | WASM sandbox |
 | `doctor` | ✅ | 🚧 | P2 | 16 subsystem checks |
-| `logs` | ✅ | ❌ | P3 | Query logs |
+| `logs` | ✅ | 🚧 | P3 | `logs` (gateway.log tail), `--follow` (SSE live stream), `--level` (get/set). No DB-persisted log history. |
 | `update` | ✅ | ❌ | P3 | Self-update |
 | `completion` | ✅ | ✅ | - | Shell completion |
 | `/subagents spawn` | ✅ | ❌ | P3 | Spawn subagents from chat |