feat(dev-proxy): reload env file changes

[lyzno1]

Summary

• enable dev-proxy watch mode by default with an opt-out --no-watch flag
• reload the running proxy when the config file or explicit --env-file changes
• keep the process stable by swapping the Hono app in place unless host/port changes

Why chokidar

• c12 watchConfig is the official config-watch path and is used for dev proxy config changes
• c12 watchConfig does not include the explicit dotenv file passed through --env-file in its watched file list
• chokidar is c12's documented watcher peer for config watching, so dev-proxy declares it directly and uses it narrowly for the env file instead of relying on an implicit transitive install or an outer process restarter

Test

• pnpm --config.verify-deps-before-run=false --filter @langgenius/dev-proxy type-check
• pnpm --config.verify-deps-before-run=false --filter @langgenius/dev-proxy test
• pnpm --config.verify-deps-before-run=false --filter @langgenius/dev-proxy build

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.99%. Comparing base (b04b444) to head (cf9e649).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #36384      +/-   ##
==========================================
- Coverage   85.99%   85.99%   -0.01%     
==========================================
  Files        4458     4458              
  Lines      211918   211893      -25     
  Branches    39544    39531      -13     
==========================================
- Hits       182232   182209      -23     
+ Misses      26471    26469       -2     
  Partials     3215     3215              

Flag	Coverage Δ
dify-ui	94.80% <ø> (ø)
web	86.57% <ø> (-0.01%)	⬇️

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