[git-hooks] Handle drifted hook replacement safely (#190)

[coisa]

Related Issue

Closes #190

Motivation / Context

• dev-tools:sync could fail during git-hooks when a drifted hook target in .git/hooks was left in an unwritable or otherwise broken state
• the previous chmod call also used the wrong numeric form, which could leave hooks with invalid permissions

Changes

• remove an existing drifted hook before copying the packaged replacement
• keep hook install failures isolated per file and return a clear command failure after processing the full hook set
• apply the executable mode with 0o755
• document the defensive rewrite behavior and failure mode in the git-hooks command docs

Verification

• composer dev-tools
• Focused command(s):
  • composer dev-tools changelog:check
  • ./vendor/bin/phpunit tests/Console/Command/GitHooksCommandTest.php
• Manual verification:
  • removed .git/hooks in this repository
  • ran php bin/dev-tools git-hooks --source=resources/git-hooks --target=.git/hooks
  • verified ls -lash .git/hooks and stat showed -rwxr-xr-x for installed hooks

Documentation / Generated Output

• README updated
• docs/ updated
• Generated or synchronized output reviewed

Changelog

• Added a notable CHANGELOG.md entry

Reviewer Notes

• .github/wiki remains a local-only change in my checkout and is intentionally not part of this PR.

[github-actions]

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