fix(diagnostics): use useDocumentText to reliably trigger diagnostics on content changes

[9romise]

#43 introduced a regression by replacing useDocumentText with activeDocument + activeDocumentVersion computed refs as the watch source, which caused diagnostics to not refresh when editing a file without switching tabs.

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📝 Walkthrough

Walkthrough

The change modifies the diagnostic collection mechanism in src/providers/diagnostics/index.ts by replacing computed properties for tracking the active document (activeDocument and activeDocumentVersion) with a useDocumentText hook imported from reactive-vscode. The trigger for collecting diagnostics now watches activeDocumentText and enabledRules as dependencies instead of the previous computed values. This adjustment removes the reliance on document.version for detecting document changes. The modification spans 3 additions and 4 deletions with no changes to public exports.

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description check	✅ Passed	The pull request description clearly explains the regression introduced in PR #43 and how this change fixes it by restoring useDocumentText.
Merge Conflict Detection	✅ Passed	✅ No merge conflicts detected when merging into main

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✨ Finishing touches

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• Post copyable unit tests in a comment
• Commit unit tests in branch fix/regression

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