feat(voyage)!: marketplace handoff — rename plugins/ultraplan-local to plugins/voyage [skip-docs]

Session 5 of voyage-rebrand (V6). Operator-authorized cross-plugin scope.

- git mv plugins/ultraplan-local plugins/voyage (rename detected, history preserved)
- .claude-plugin/marketplace.json: voyage entry replaces ultraplan-local
- CLAUDE.md: voyage row in plugin list, voyage in design-system consumer list
- README.md: bulk rename ultra*-local commands -> trek* commands; ultraplan-local refs -> voyage; type discriminators (type: trekbrief/trekreview); session-title pattern (voyage:<command>:<slug>); v4.0.0 release-note paragraph
- plugins/voyage/.claude-plugin/plugin.json: homepage/repository URLs point to monorepo voyage path
- plugins/voyage/verify.sh: drop URL whitelist exception (no longer needed)

Closes voyage-rebrand. bash plugins/voyage/verify.sh PASS 7/7. npm test 361/361.

plugins/ultraplan-local/tests/fixtures/session-state/valid-in-progress.json

@@ -1,8 +0,0 @@
-{
-  "schema_version": 1,
-  "project": ".claude/projects/2026-05-01-example-multisession",
-  "next_session_brief_path": ".claude/projects/2026-05-01-example-multisession/brief.md",
-  "next_session_label": "Session 2: Implement validator + tests",
-  "status": "in_progress",
-  "updated_at": "2026-05-01T18:00:00.000Z"
-}