grep/glob ignore run cancellation, leaving Zero unresponsive to Ctrl+C and /exit

[euxaristia]

Adding issue-approved label as required for community PRs (per reviews on #464).

[euxaristia]

Per reviews on PR #464 (and others), this issue needs the \issue-approved\ label to allow community PRs to proceed with code review.

Requesting core team to review and add the label if approved.

Related PRs: #464, #468, etc.

[euxaristia]

Requesting the issue-approved label per CONTRIBUTING.md so review on #464 can proceed.

Issue scope: grep and glob discard their context and can keep walking after the TUI marks a run cancelled, which blocks Ctrl+C and /exit until the process is killed.

PR: #464 (Fixes #466)

Status:

• Code changes are on fix/grep-glob-context-cancellation (head a3d79b8): ctx is threaded through grep/glob walks and collectGrepMatches, with cancellation tests.
• CI is fully green on the latest run, including Smoke (windows-latest).
• jatmn's remaining review note is only the missing issue-approved label on this issue.

Happy to adjust scope or add detail if maintainers want anything else before approval.