Label realtime and trace diagnostics

[rogierx]

Addresses #50.

This makes tsperf diagnostics identify which measurement pipeline produced them:

• realtime diagnostics now show Realtime tsserver: ... and use source tsperf realtime
• trace-file diagnostics now show Trace check: ... and use source tsperf trace
• both paths use stable diagnostic codes instead of the old ambiguous numeric realtime code

That should make confusing warnings easier to triage, especially when deciding whether a warning came from trace metrics or realtime tsserver measurements.

The branch also removes package-manager caching from the tag-triggered release workflow so the publish/release path does not rely on shared caches.

Validation:

• pnpm exec vitest run test/index.test.ts
• pnpm run typecheck
• pnpm exec eslint src/diagnosticText.ts src/index.ts src/traceDiagnostics.ts test/index.test.ts
• pnpm exec rollup -c
• git diff --check