[CV-10]: [Enhancement] Auto-Refresh Coverage When Test Files Are Saved

[kool7]

• Added automatic pytest re-run when any test file is saved or deleted — coverage dashboard and status bar update within 2 seconds, with no manual steps required.
• Added a spinner in the status bar while pytest runs so users always know coverage is being refreshed, not frozen.
• Added a coverageVisualizer.autoRunOnTestChange setting (default on) so users with slow test suites can opt out without losing other features.
• Fixed dashboard not opening after "Show Dashboard" triggers a pytest run — previously the panel stayed blank until the command was run a second time.
• Fixed coverage percentage showing 100% instead of the correct value — the extension now always generates coverage data via coverage json from .coverage, which respects the project's branch coverage configuration.
• Fixed dashboard not refreshing after auto-run completes — the panel now always shows the latest numbers without needing to clear and reload manually.
• Improved extension stability — running pytest process is killed on deactivation, environment checks are cached after first run, and process-level race conditions are prevented.

[kool7]

Looks good