feat: `cora affected` — Find tests affected by changes

[ajianaz]

Description

Find test files affected by source code changes. Designed for CI integration.

cora affected src/auth.ts src/api.ts         # pass changed files
git diff --name-only | cora affected --stdin  # pipe from git diff
cora affected src/auth.ts --filter "e2e/*" # custom test file pattern

Why

CI/CD integration — know which tests to run after a change. CodeGraph has codegraph affected as a key feature. Cora adds LLM-assisted reasoning about test coverage gaps.

Scope

• Dependency graph traversal from changed files → test files
• Configurable test file detection patterns
• Stdin support for piping from git diff
• JSON output for CI integration
• --filter glob for test file patterns

Depends On

• feat: cora index — Symbol index & SQLite persistence #264 cora index
• feat: cora callers / cora impact — Call graph query commands #266 cora callers / cora impact

Strategy Ref

Code intelligence strategy #6 from competitive analysis.