chore: clean up clear-cut ESLint warnings (#732) (#734)

Pay down pre-existing error→warn lint debt. Removes dead imports/vars, unused functions, redundant regex/string escapes, and stale eslint-disable directives; converts unused `catch (_e)` to optional catch binding (src/*.cts).

No behavior change. Lint 345→125 warnings (0 errors); deferred categories (n/no-process-exit, test-sleeps, control-regex) tracked in #732 for follow-up. Full test suite green (0 failures); code-review verified all removals unused and all escape fixes semantics-preserving.

Closes #732

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

src/workstream-inventory.cts

@@ -17,7 +17,7 @@ import fs from 'node:fs';
 import path from 'node:path';
 // eslint-disable-next-line @typescript-eslint/no-require-imports
 import core = require('./core.cjs');
-const { toPosixPath, readSubdirectories } = core;
+const { readSubdirectories } = core;
 // eslint-disable-next-line @typescript-eslint/no-require-imports
 import planScan = require('./plan-scan.cjs');
 // eslint-disable-next-line @typescript-eslint/no-require-imports
@@ -163,7 +163,6 @@ function getOtherActiveWorkstreamInventories(cwd: string, excludeWs: string): Wo
     .filter(inventory => !isCompletedInventory(inventory.status));
 }
 
-// Re-export toPosixPath for compatibility (used by callers indirectly through core)
 export = {
   countPhaseFiles,
   countRoadmapPhases,