reuse files when generate report within hardlinks(#545)

[todti]

reduces disk usage and I/O when generating multiple reports into the same output directory by reusing identical files via hardlinks instead of writing duplicates.

• Adds content-hash based deduplication in FileSystemReportFiles with atomic tmp+rename and a safe fallback to regular writes when hardlinking isn’t possible.
• Adds unit tests and an e2e check ensuring shared static assets and attachments remain accessible across multiple awesome reports (inode check on non-Windows).

Caveats / coverage notes

• The tricky case is cache invalidation: if a path that was used as the canonical file for some content hash is later rewritten with different content, the old hash must stop pointing at that path. The implementation now drops that stale canonical mapping before writing the new file, and the unit suite covers the old content -> new content -> old content at another path scenario.
• Writes and hardlink replacements go through a temporary file followed by rename, so readers should not observe a partially written target file.
• Hardlinking can fail on some filesystems or environments (for example cross-device output, permissions, or missing canonical source). Those errors are treated as recoverable and fall back to a regular write.
• Inode assertions are only meaningful on non-Windows platforms, so tests check inode reuse conditionally. On Windows the tests still validate that every report path remains readable and has the expected content.
• The e2e coverage focuses on the multi-awesome-report case: shared static assets and global attachments must stay accessible from both report directories while avoiding duplicate inodes where the platform supports it.

refer to #545 #486

[github-actions]

Allure Report Summary

	Name	Duration	Stats	New	Flaky	Retry	Report
	Allure 3 Report	25m 21s	1440    12    15	9	0	0	View
	My Dashboard	25m 21s	1440    12    15	9	0	0	View
	Allure 3 GitHub actions run (2026-05-29T18:21:37.609Z)	25m 21s	1440    12    15	9	0	0	View

[jrett2]

FYI this is a duplicate of #486