ci: enforce 500 kB gzip per-chunk budget on every PR

[adm01-debug]

Summary

Implements the CI gate suggested in docs/BUNDLE_ANALYSIS.md (PR #31) as a standalone workflow. Enforces a hard upper bound of 500 kB gzip per chunk on every PR touching src/, package.json, the lockfile, or the Vite/TS configs.

Why hard 500 kB

500 kB gzip is the threshold where 4G mobile TTI starts to degrade meaningfully (web.dev — Performance budgets 101). Single chunks above that are the kind of regression that warrants review before merge, not a post-merge cleanup task. Hence hard error, not warn.

What the job does

1. npm ci + vite build
2. Walks dist/assets/*.js, computes gzip size of each chunk
3. Reports total, largest chunk, count
4. Exits 1 if any chunk > 500 kB gzip and prints fix strategies (lazy-loading via React.lazy, manualChunks in vite.config.ts, lucide-react tree-shaking)
5. Always writes a step summary with the top 16 chunks by raw size — reviewers see the bundle shape in the PR Checks tab without rerunning locally

Self-contained

The check is inlined as a node --input-type=module script so this workflow doesn't depend on scripts/bundle-analysis.mjs (which lives in PR #31). Either PR can land first.

Triggers

• pull_request against main — only when files that affect the bundle change
• push to main — so main HEAD always has a green budget marker visible

Validation

Tested the inline script against the current dist/:

Total: 2971.9 kB gzip across 294 chunks
Largest chunk: export-vendor = 181.8 kB gzip
✅ all 294 chunks ≤ 500 kB gzip

YAML validates with python -c 'import yaml; yaml.safe_load(...)'.

Test plan

• After merge: open a test PR that adds a 600 kB import (e.g., import lodash from 'lodash'); confirm the workflow fails with the expected message
• Confirm the step summary populates in the PR Actions tab

https://claude.ai/code/session_01KWeDG

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