Fix omnidev restart loop on Linux from non-mutating file access events

[Leemoonsoo]

Related issue

Closes #4328

Summary

• On Linux, omnidev's file watcher treated every filesystem event on a watched .py path as a source change — including non-mutating access/open events. Python imports at backend startup emit access events, so each freshly started backend immediately re-triggered a reload, producing a continuous restart loop (~every 2.6s) with no actual edits.
• Fix: only reload on mutating event kinds (create / modify / remove) in dev/omnidev/src/watcher.rs, via a new is_mutating() helper; non-mutating events are skipped (and logged in debug mode).

Test Plan

• cargo test -p omnidev (focused binary suite): 38 tests pass, including two new regression tests — mutating_events_trigger_reload and access_events_do_not_trigger_reload.
• Manually verified on Ubuntu 24.04: after installing the patched binary, omnidev no longer restarts the backend/host on startup or on file reads; reloads still fire on real edits.

Demo

Before

omnidev-before.mov

After

omnidev-after.mov

Type of change

• Bug fix
• Feature
• UI / frontend change
• Refactor / chore
• Docs
• Test / CI
• Breaking change

Test coverage

• Unit tests added / updated
• Integration tests added / updated
• E2E tests added / updated
• Manual verification completed
• Existing tests cover this change
• Not applicable

Coverage notes

Added unit tests covering event-kind classification (mutating vs. access). Manually verified on Ubuntu 24.04 that the restart loop is gone and that real edits still trigger a reload.

Changelog

Fix omnidev restart loop on Linux caused by non-mutating file access events

[github-actions]

@Leemoonsoo This PR is a Bug fix, Feature, or UI / frontend change but the Demo section is missing or only contains a placeholder.

These change types require a screenshot or screen recording so reviewers can see the new behaviour without checking out the branch. Please update the Demo section with:

• A screenshot or screen recording of the change, or
• A link to a hosted video or GIF showing the new behaviour.

Use N/A only when the change has no user-visible effect whatsoever (e.g. a pure refactor or test-only change). If that's the case, uncheck the relevant type box and check Refactor / chore or Test / CI instead.

[Leemoonsoo]

Updated Demo video before / after