fix: stop EnsureAllMetadata oscillating when two DBs map to same rig

[quad341]

Summary

• Groups databases by rig in EnsureAllMetadata — processes each rig exactly once
• When multiple DB candidates exist for a rig, prefers the value already in metadata.json to avoid repair churn
• Adds TestEnsureAllMetadata_NoOscillation regression test

Test plan

• gt up no longer prints oscillating metadata repair warnings
• Fresh install picks correct database name
• Existing installs with valid metadata.json are left unchanged

🤖 Generated with Claude Code

[codecov-commenter]

❌ 5 Tests Failed:

Tests completed	Failed	Passed	Skipped
9320	5	9315	48

View the top 3 failed test(s) by shortest run time

github.com/steveyegge/gastown/internal/cmd::TestBuildRefineryPatrolVars_FullConfig

Stack Traces | 0s run time

=== RUN   TestBuildRefineryPatrolVars_FullConfig
    patrol_helpers_test.go:166: expected 5 vars, got 7: [target_branch=main integration_branch_refinery_enabled=true integration_branch_auto_land=false run_tests=true delete_merged_branches=true judgment_enabled=false review_depth=standard]
--- FAIL: TestBuildRefineryPatrolVars_FullConfig (0.00s)

github.com/steveyegge/gastown/internal/cmd::TestRunHooksSyncNonClaudeAgent

Stack Traces | 0s run time

=== RUN   TestRunHooksSyncNonClaudeAgent
Syncing hooks...
  ✓ mayor/.claude/settings.json (created)
  ✓ deacon/.claude/settings.json (created)
  ✓ myrig/crew/.claude/settings.json (created)
warning: role_agents[crew]=opencode - agent "opencode" binary "opencode" not found in PATH, falling back to default

Synced 3 targets (3 created, 0 updated, 0 unchanged)
    hooks_sync_test.go:366: opencode plugin not created in worktree alice
--- FAIL: TestRunHooksSyncNonClaudeAgent (0.00s)

github.com/steveyegge/gastown/internal/doctor::TestHooksSyncCheck_Fix_TemplateAgent

Stack Traces | 0.01s run time

=== RUN   TestHooksSyncCheck_Fix_TemplateAgent
warning: role_agents[crew]=opencode - agent "opencode" binary "opencode" not found in PATH, falling back to default
    hooks_sync_check_test.go:219: expected StatusWarning before fix, got OK
--- FAIL: TestHooksSyncCheck_Fix_TemplateAgent (0.01s)

github.com/steveyegge/gastown/internal/doctor::TestHooksSyncCheck_TemplateAgent_Missing

Stack Traces | 0.01s run time

=== RUN   TestHooksSyncCheck_TemplateAgent_Missing
warning: role_agents[crew]=opencode - agent "opencode" binary "opencode" not found in PATH, falling back to default
    hooks_sync_check_test.go:193: expected StatusWarning for missing template agent file, got OK: All 3 hook targets in sync
--- FAIL: TestHooksSyncCheck_TemplateAgent_Missing (0.01s)

github.com/steveyegge/gastown/internal/doctor::TestHooksSyncCheck_TemplateAgent_OutOfSync

Stack Traces | 0.01s run time

=== RUN   TestHooksSyncCheck_TemplateAgent_OutOfSync
warning: role_agents[crew]=opencode - agent "opencode" binary "opencode" not found in PATH, falling back to default
    hooks_sync_check_test.go:172: expected StatusWarning for out-of-sync template agent, got OK: All 3 hook targets in sync
--- FAIL: TestHooksSyncCheck_TemplateAgent_OutOfSync (0.01s)

To view more test analytics, go to the Test Analytics Dashboard
_{📋 Got 3 mins? Take this short survey to help us improve Test Analytics.}