fix: prevent deadlock when cross-region CDK stacks share the same stack name

[go-to-k]

Problem

delstack cdk deadlocks when two cross-region stacks share the same CloudFormation stack name:

INF Cross-region dependencies detected. Deleting stacks in dependency order...
fatal error: all goroutines are asleep - deadlock!

This happens with a common CDK pattern: a CloudFront us-east-1 support stack reuses the main stack's CloudFormation name via the stackName property. Both stacks resolve to the same StackName (e.g. AiApi), living in different regions.

Root cause

CdkDeleter builds its reverse-topological dependency graph keyed by StackName. When two distinct stacks share a name:

1. stackMap collapses to a single entry.
2. The main stack's dependency on the support stack resolves (by name) to the shared key, giving reverseInDegree == 1.
3. No stack ever reaches in-degree 0, so no initial deletion starts and the completion loop blocks forever.

Additionally, Dependencies were stored as resolved stack names, which are ambiguous when names collide across regions.

Fix

Use the unique Cloud Assembly artifact key as the graph identity:

• StackInfo gains an Identifier field, and Dependencies now hold artifact keys instead of resolved stack names.
• CdkDeleter keys its graph by identity (stackIdentity, falling back to StackName when unset) and deletes by StackName + Region.
• Stack selection (-s) dedups by identity, fixing a related latent bug where only one of two same-named cross-region stacks was selectable.

Tests

• TestCdkDeleter_DeleteStacks_CrossRegionDeps_SameStackName reproduces the reported deadlock using a mock executor (no real AWS calls).
• TestParseManifest_CrossRegionSameStackName covers parsing a manifest where stackName override causes a name collision.
• Existing dependency/selection assertions updated for the artifact-key identity.

No real stacks were deleted during verification; the regression test with mocks confirms the fix.