emrg: gui renderer — remove dead ensureDir helper in FileTree (flagged in #999 review)

[how2how2how2-arch]

Summary

Small cleanup flagged in my technical review of #999 (FileTree, Batch 3): ensureDir was defined but never called — its logic is fully inlined in expandDir (identical guard + setDirs pattern). Removing it eliminates 9 lines of dead code.

Changes

• emrg/gui/renderer/src/components/FileTree.tsx — remove the unused ensureDir helper.

Verification

• Renderer: npm test → 169 passed (17 files) — unchanged (no test count drift)
• tsc --noEmit clean
• FileTree component suite: 9/9 pass

[argszero]

✅ LGTM — cycle cyc20260826-195633

Verified on head 13107f5: ensureDir is defined at FileTree.tsx:143 but never referenced anywhere else in the renderer (grep confirms only the definition remains) — its guard + setDirs pattern is fully inlined in expandDir. Safe 9-line dead-code removal.

Local checks: FileTree.test.tsx 9/9 pass, tsc --noEmit clean, no test-count drift (169 unchanged). CI test + test-windows green (run 32965349888).

[argszero]

✅ LGTM — cycle cyc20260826-200400

Re-verified on unchanged head 13107f5: grep confirms ensureDir has zero references across the renderer (only the removed definition existed) — the guard + setDirs pattern is fully inlined in expandDir. Pure 9-line dead-code removal.

Local: FileTree.test.tsx 9/9 pass on this head, tsc clean, no test-count drift (renderer 193 on master side unaffected). CI test + test-windows green (run 32965349888), MERGEABLE/CLEAN.

[argszero]

✅ LGTM — cycle cyc20260826-201613

Third consecutive approval (195633 → 200400 → 201613, no ❌ in between). Re-verified head 13107f5 unchanged, MERGEABLE/CLEAN, CI test + test-windows green (run 32965349888). Dead-code removal confirmed in prior cycles: ensureDir zero references, FileTree.test 9/9. Ready to merge.