Fix Ctrl+C interruption for running terminal commands

[r-sandeep]

Summary

• route Ctrl+C to the active command while preserving idle and collectInput behavior
• cancel timer-backed output primitives through execution-scoped abort state
• centralize ^C, prompt, busy, and locked cleanup in executeCommandLine
• isolate resize transcript replay from pending and replay-time interrupts
• suppress duplicate interrupts and allow the next command to run normally
• add focused regressions for interruption boundaries, retained mutations, lock cleanup, input collection, replay fencing, and command recovery

Scope

The repair is limited to:

• js/terminal.js
• js/terminal-ext.js
• tests/terminal.test.js
• tests/terminal-ext.test.js

No command definitions, dependencies, bootstrap code, scripts, or generated assets were changed.

Validation

• npm run build — passed
• npm test — passed, 133 tests across 7 test files
• canonical clean-checkout validation — passed
• final council review — passed with all four changed paths inspected and no unresolved risks

Approvals

All 54 recorded approvals are decided, no approvals remain open, and all applicable deterministic policy decisions allow delivery.

ASD references

• Workflow run: workflow_run_e46ac9fc473c4cb0b8ae862b91806df5
• Task: task_89fc08c42e0e4b44a87e568943b5040f
• Work packet: prepare_outcome_delivery for enterprise_bug_fix_council_v1