chore: remove stale debug-copy + drop placeholder string-split hack; v4.11.1

- Remove untracked root-level flowchart-bundle.js (older v4.10.0 copy
  that had drifted from src/renderer/flowchart-bundle.js; never loaded
  by Electron, just repo noise).
- In src/renderer/flowchart-bundle.js, replace the runtime
  concatenation "'place' + 'holder'" with the proper 'placeholder'
  attribute at the two label-input call sites (node + edge) and
  remove the now-stale comment explaining the hack. No functional
  change.
- Bump version 4.11.0 -> 4.11.1 in package.json and README.md and add
  the matching UPDATES.md entry.

Verification:
- npm run lint          clean
- npm run format:check  clean
- npm test              92/92 suites, 1143/1143 tests pass on this run
- PDFBatchOperations.test.js passes 21/21 in isolation
  (the occasional failure seen in the v4.11.0 run was a parallel-test
  file-IO race, not introduced by these changes)

Amit Haridas

UPDATES.md

@@ -1,5 +1,12 @@
 # PanConverter - Updates & Changelog
 
+## Version 4.11.1 (2026-09-15)
+
+### Chore
+
+- **Cleanup: removed stale debug-copy `flowchart-bundle.js` from project root.** The root-level file was an older v4.10.0 copy that had drifted from `src/renderer/flowchart-bundle.js` (now v4.11.0); the canonical bundle lives under `src/renderer/`, the root copy was never loaded by Electron and was just repo noise.
+- **Cleanup: replaced `'place' + 'holder'` string-split hack with proper `'placeholder'` attribute.** The v4.10.0 / v4.11.0 bundles deliberately concatenated the attribute name at runtime to evade a static-source grep for the literal word "placeholder". The HTML attribute name itself is the standard HTML spec — no need to obfuscate it. Two call sites (node label input, edge label input) now use `.setAttribute('placeholder', 'Label')` directly. (No functional change.)
+
 ## Version 4.11.0 (2026-09-15)
 
 ### Feat