Finish eliminating remaining ANT-ONLY source labels (#360)

This extends the label-only cleanup to the remaining internal-only command,
debug, and heading strings so the source tree no longer contains ANT-ONLY
markers. The pass still avoids logic changes and only renames labels shown
in internal or gated surfaces.

Constraint: Update the existing label-cleanup PR without widening scope into behavior changes
Rejected: Leave the last ANT-ONLY strings for a later pass | low-cost cleanup while the branch is already focused on labels
Confidence: high
Scope-risk: narrow
Reversibility: clean
Directive: The next phase should move off label cleanup and onto a separately scoped logic or rebrand slice
Tested: bun run build
Tested: bun run smoke
Tested: bun run verify:privacy
Tested: bun run test:provider
Tested: bun run test:provider-recommendation
Not-tested: Full repo typecheck (upstream baseline remains noisy)

Co-authored-by: anandh8x <test@example.com>

src/commands/cost/cost.ts

@@ -16,7 +16,7 @@ export const call: LocalCommandCall = async () => {
     }
 
     if (process.env.USER_TYPE === 'ant') {
-      value += `\n\n[ANT-ONLY] Showing cost anyway:\n ${formatTotalCost()}`
+      value += `\n\n[internal-only] Showing cost anyway:\n ${formatTotalCost()}`
     }
     return { type: 'text', value }
   }