feat: opt-in polecat self-terminate after gt done (with cleanup fix)

[dannomayernotabot]

I KNOW YOU ALREADY CHAGNED THIS BUT HEAR ME OUT

i saw
https://discord.com/channels/1462817445562814505/1462953549838291045/1475601173812740129

we have been discussing in troubleshooting, starting around here https://discord.com/channels/1462817445562814505/1462951684551737509/1486363653489037552

this is the latest summary of the issues and why i am wanting these changes:
polecat-session-deaths (1).md

its entirely possible im just using gastown wrong, i probably am, but i cannot figure out how to make all of these polecat deaths reliably cease without making them ephemeral. this is half pr half cry for help

Summary

• Add polecat_self_terminate config option (default: false) under operational.daemon
• When enabled, polecats kill their session after gt done completes instead of transitioning to IDLE
• Fix: Self-terminate now fires AFTER all cleanup (branch push, MR submit, worktree sync) — original placement fired mid-cleanup, leaving orphaned worktree directories

Supersedes #3295 (same feature, adds the cleanup timing fix).

Test plan

• go build ./... passes
• Tested with 26 concurrent polecats — zero deaths, all beads completed
• Verify worktree directories are cleaned up after self-terminate

Generated with Claude Code

[codecov-commenter]

❌ 5 Tests Failed:

Tests completed	Failed	Passed	Skipped
9319	5	9314	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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