fix(pool): create sessions with concrete identity

[julianknutsen]

Summary

• create new pool session beads with their concrete slot identity immediately
• stamp agent_name, alias, pool_slot, title, and agent label consistently at creation time
• keep existing fallback behavior for callers that do not know a concrete pool identity

Tests

• go test ./cmd/gc -run 'TestBuildDesiredState_NewPoolSessionBeadCreatedWithConcreteIdentity|TestBuildDesiredState_RoutedQueueDoesNotCreateOneSessionPerBead|TestSelectOrCreatePoolSessionBead|TestSelectOrCreateDependencyPoolSessionBead|TestPoolSessionName|TestCreatePoolSessionBead' -count=1
• go test ./cmd/gc -count=1
• pre-commit quality gate during commit: lint, vet, observable go test

---

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• Let Codesmith autofix CI failures and bot reviews

[codecov-commenter]

Codecov Report

❌ Patch coverage is 79.54545% with 9 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
cmd/gc/build_desired_state.go	70.96%	5 Missing and 4 partials ⚠️

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[blacksmith-sh]

Found 1 test failure on Blacksmith runners:

Failure

Test	View Logs
github.com/gastownhall/gascity/cmd/gc/ TestCityRuntimeManualReloadReplyWaitsForTickCompletion	View Logs

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