Make hash IDs opt-in via id_mode config (bd-5404)

- Add id_mode config (sequential|hash), defaults to sequential
- Update CreateIssue/CreateIssues to check id_mode and generate appropriate IDs
- Implement lazy counter initialization from existing issues
- Update migrate --to-hash-ids to set id_mode=hash after migration
- Fix hash ID tests to set id_mode=hash
- Fix renumber test to use explicit IDs
- All 183 test packages pass

This makes hash IDs backward-compatible opt-in rather than forced default.

.beads/beads.jsonl

@@ -130,6 +130,8 @@
 {"id":"bd-5403defc.1","content_hash":"d1ffe0d966939abf9449b6157cf9fcf42342b3056bfa65aeffbfa913ff722928","title":"Child test","description":"","status":"closed","priority":2,"issue_type":"task","created_at":"2025-10-30T15:46:47.841563-07:00","updated_at":"2025-10-30T15:46:59.618715-07:00","closed_at":"2025-10-30T15:46:59.618715-07:00"}
 {"id":"bd-5403defc.1.1","content_hash":"f835dedf00bec5edfac81de035e4b5af1490afa7008bdf74683041c44d33d830","title":"Nested child","description":"","status":"closed","priority":2,"issue_type":"task","created_at":"2025-10-30T15:46:51.064625-07:00","updated_at":"2025-10-30T15:46:59.618994-07:00","closed_at":"2025-10-30T15:46:59.618994-07:00"}
 {"id":"bd-5403defc.1.1.1","content_hash":"0c150383d4c2ce7aeecf70fe53f2599e9720eccffc7ab717a2abfef8e37f9dcc","title":"Deep nested","description":"","status":"closed","priority":2,"issue_type":"task","created_at":"2025-10-30T15:46:53.570315-07:00","updated_at":"2025-10-30T15:46:59.619236-07:00","closed_at":"2025-10-30T15:46:59.619236-07:00"}
+{"id":"bd-5404","content_hash":"71db1274320e28acd735902b9c07c2683b0c7dcbd7808637457dcb492273f19f","title":"Hash IDs as default: testing, release, and migration","description":"Drive hash IDs to be the default for Beads. Currently on feature/hash-ids branch, opt-in via --to-hash-ids flag, requires explicit migration. Target repos: ~/src/fred/beads, ~/wyvern, ~/src/wyvern. Deployment: homebrew/bin, MCP servers, all daemons at 0.19.1","design":"1. Checkout feature/hash-ids 2. Bump to 0.19.1 on branch 3. Build/install to homebrew 4. Update MCP servers 5. Restart daemons 6. Migrate all repos 7. Test workers 8. Make hash IDs default 9. Verify","acceptance_criteria":"All 3 repos migrated, all daemons at 0.19.1, workers functional, hash IDs default","status":"open","priority":1,"issue_type":"epic","created_at":"2025-10-30T16:33:07.965639-07:00","updated_at":"2025-10-30T16:33:07.965639-07:00"}
+{"id":"bd-5405","content_hash":"4c12ad67469db8ac3b9a9d6199c78521202b54a5cb4c0571ea1fb5e4cd8d42bc","title":"Test mixed ID system","description":"","status":"open","priority":2,"issue_type":"task","created_at":"2025-10-30T16:36:18.414852-07:00","updated_at":"2025-10-30T16:36:18.414852-07:00"}
 {"id":"bd-55","content_hash":"d4d20e71bbf5c08f1fe1ed07f67b7554167aa165d4972ea51b5cacc1b256c4c1","title":"Split internal/rpc/server.go into focused modules","description":"The file `internal/rpc/server.go` is 2,273 lines with 50+ methods, making it difficult to navigate and prone to merge conflicts. Split into 8 focused files with clear responsibilities.\n\nCurrent structure: Single 2,273-line file with:\n- Connection handling\n- Request routing\n- All 40+ RPC method implementations\n- Storage caching\n- Health checks \u0026 metrics\n- Cleanup loops\n\nTarget structure:\n```\ninternal/rpc/\n├── server.go          # Core server, connection handling (~300 lines)\n├── methods_issue.go   # Issue operations (~400 lines)\n├── methods_deps.go    # Dependency operations (~200 lines)\n├── methods_labels.go  # Label operations (~150 lines)\n├── methods_ready.go   # Ready work queries (~150 lines)\n├── methods_compact.go # Compaction operations (~200 lines)\n├── methods_comments.go # Comment operations (~150 lines)\n├── storage_cache.go   # Storage caching logic (~300 lines)\n└── health.go          # Health \u0026 metrics (~200 lines)\n```\n\nMigration strategy:\n1. Create new files with appropriate methods\n2. Keep `server.go` as main file with core server logic\n3. Test incrementally after each file split\n4. Final verification with full test suite","acceptance_criteria":"- All 50 methods split into appropriate files\n- Each file \u003c500 LOC\n- All methods remain on `*Server` receiver (no behavior change)\n- All tests pass: `go test ./internal/rpc/...`\n- Verify daemon works: start daemon, run operations, check health\n- Update internal documentation if needed\n- No change to public API","status":"closed","priority":1,"issue_type":"task","created_at":"2025-10-28T14:21:37.51524-07:00","updated_at":"2025-10-28T14:21:37.51524-07:00","closed_at":"2025-10-28T14:11:04.399811-07:00"}
 {"id":"bd-57","content_hash":"3ab290915c117ec902bda1761e8c27850512f3fd4b494a93546c44b397d573a3","title":"bd resolve-conflicts - Git merge conflict resolver","description":"Automatically resolve JSONL merge conflicts.\n\nModes:\n- Mechanical: ID remapping (no AI)\n- AI-assisted: Smart merge/keep decisions\n- Interactive: Review each conflict\n\nHandles \u003c\u003c\u003c\u003c\u003c\u003c\u003c conflict markers in .beads/beads.jsonl\n\nFiles: cmd/bd/resolve_conflicts.go (new)","status":"closed","priority":1,"issue_type":"task","created_at":"2025-10-28T14:48:17.457619-07:00","updated_at":"2025-10-28T15:47:33.037021-07:00","closed_at":"2025-10-28T15:47:33.037021-07:00"}
 {"id":"bd-58","content_hash":"04b157cdc3fb162be6695517c10365c91ed14f69fad56a7bfc2b88d6b742ac38","title":"bd repair-deps - Orphaned dependency cleaner","description":"Find and fix orphaned dependency references.\n\nImplementation:\n- Scan all issues for dependencies pointing to non-existent issues\n- Report orphaned refs\n- Auto-fix with --fix flag\n- Interactive mode with --interactive\n\nFiles: cmd/bd/repair_deps.go (new)","status":"open","priority":1,"issue_type":"task","created_at":"2025-10-29T19:42:29.852745-07:00","updated_at":"2025-10-29T19:42:29.852745-07:00"}