feat: add default_formula rig config for sling dispatch

[totalslacker]

Summary

• Adds default_formula to rig property layers so gt sling uses the rig's configured formula instead of always defaulting to mol-polecat-work
• Enables per-project formula configuration: gt rig config set myrig default_formula mol-custom
• --formula flag still overrides the configured default
• Resolution order: explicit flag > rig property layers (wisp/bead) > rig settings file > hardcoded fallback

Motivation

Different projects may need different default formulas for their polecats. Currently the only way to use a non-default formula is to pass --formula on every gt sling invocation, which is error-prone. A per-rig config eliminates this.

Test plan

• TestResolveFormula — 6 subtests covering precedence: explicit flag, hookRawBead, system default, wisp layer override, explicit overrides wisp, empty rigName fallback
• Manual: gt rig config set <rig> default_formula <formula> persists and is picked up by gt sling
• Manual: --formula flag still overrides the default

🤖 Generated with Claude Code

[codecov-commenter]

❌ 5 Tests Failed:

Tests completed	Failed	Passed	Skipped
9326	5	9321	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 | 0.01s 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 (0.01s)

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)

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