fix(events): preserve a non-UTF-8 config.toml on hook install/teardown

[marcelsafin]

Description

_merge_toml_fragment() and _remove_toml_entries() read the user's config.toml (Codex hooks) with bare read_text() calls, so a non-UTF-8 (or otherwise unreadable) file crashes install_integration_events() and remove_integration_events() with a raw UnicodeDecodeError — and the merge path regenerates the file from what it read, so it would have discarded the user's bytes had it not crashed first. Every JSON merge/remove path already goes through _load_user_json(), which skips on an unreadable file precisely to preserve user content (#22).

Fix:

• merge: abort and return False so the caller skips tracking the untouched file (same S5 contract as _merge_copilot_json), leaving the user's bytes intact;
• teardown: skip the cleanup with a warning instead of crashing — the file contains only user content as far as we can tell, and the caller drops the manifest claim either way (S9).

Testing

• Tested locally with uv run specify --help
• Ran existing tests with uv sync && uv run pytest (6,311 passed, 176 skipped)
• Two new regression tests (install with pre-existing non-UTF-8 config.toml, teardown after the config was rewritten as non-UTF-8; both fail on main, pass with fix)
• ruff check src tests clean

AI Disclosure

• I did not use AI assistance for this contribution
• I did use AI assistance (describe below)

Implemented autonomously by GitHub Copilot CLI (model: Claude Fable 5) under human direction; TDD (failing test first), full suite and lint verified locally. Commit includes Assisted-by/Co-authored-by trailers.

[Copilot]

Pull request overview

Prevents Codex hook installation and teardown from corrupting or crashing on unreadable/non-UTF-8 user configuration.

Changes:

• Safely skips TOML merge and cleanup when decoding fails.
• Avoids manifest tracking for skipped merges.
• Adds install and teardown regression tests.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/specify_cli/events.py	Handles unreadable TOML while preserving user content.
tests/integrations/test_events.py	Tests byte preservation during install and teardown.

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