[storage] Expand CRC Fix Scope

[patrick-ogrady]

#3837 fixes the original same-page partial shrink case: an already-persisted partial tail can be resized to a shorter partial length without making the page unrecoverable if the CRC rewrite is interrupted.

This PR covers the related cases that #3837 does not cover: shrink targets that land inside a page which was previously full, and therefore was not represented by partial_page_state.

Concretely, this adds crash-safety for:

• full page -> partial page, for example PAGE_SIZE -> 45
• multi-page shrink landing inside a previously full page, for example 3 * PAGE_SIZE -> PAGE_SIZE + 45

Those target pages already have valid CRC records on disk, but #3837's protected path only ran when the target page was the current persisted partial tail. Without this PR, the fallback path can later rewrite the landing page as a padded partial page; if that write partially lands before the shorter CRC is durable, recovery can reject the landing page and truncate to the previous page boundary.

This PR fixes that by reading and validating the target page to recover the CRC record that actually committed it, then using the same two-phase CRC transition for any shrink whose target has nonzero partial bytes. If later physical pages need to be truncated first, that truncation is synced before the landing page's shorter CRC is staged.

The implementation also removes the now-unreachable later partial-tail reload path: after the CRC-safe partial_bytes > 0 branch returns, the remaining resize path is page-aligned shrink only.

Testing:

• Adds full-page-to-partial interrupted CRC stage/invalidation regressions.
• Adds multi-page-to-partial interrupted CRC stage/invalidation regressions.
• Verified with just test -p commonware-runtime resize_same_page_shrink_survives_interrupted_crc_stage resize_same_page_shrink_survives_interrupted_crc_invalidation resize_full_page_to_partial resize_multi_page_to_partial.

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Status	Name	Latest Commit	Updated (UTC)
✅ Deployment successful! View logs	commonware-mcp	6177fca	May 20 2026, 07:11 AM

[github-actions]

Benchmark results

Tip

✅ PASSED: No benchmark exceeded the regression threshold.

Benchmark comparison table

Benchmark	Baseline (main)	Current	Delta	Threshold	Status
qmdb::merkleize/variant=any::unordered::fixed::mmr keys=10000 ch=false sync=false	1.567 ms	1.581 ms	+0.91%	10.00%	✅ PASS
qmdb::merkleize/variant=current::ordered::fixed::mmb chunk=256 keys=10000 ch=true sync=false	3.100 ms	3.063 ms	-1.20%	10.00%	✅ PASS

Baseline commit(s): 14a016a55f43

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Latest commit:	6177fca
Status:	✅  Deploy successful!
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[codecov]

Codecov Report

❌ Patch coverage is 98.23009% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.74%. Comparing base (fd03283) to head (6177fca).

Files with missing lines	Patch %	Lines
runtime/src/utils/buffer/paged/append.rs	98.07%	1 Missing and 1 partial ⚠️

@@                        Coverage Diff                        @@
##           codex/append-resize-crc-fallback    #3839   +/-   ##
=================================================================
  Coverage                             95.73%   95.74%           
=================================================================
  Files                                   473      473           
  Lines                                192765   192841   +76     
  Branches                               4676     4672    -4     
=================================================================
+ Hits                                 184548   184630   +82     
+ Misses                                 6645     6642    -3     
+ Partials                               1572     1569    -3     

Files with missing lines	Coverage Δ
runtime/src/utils/buffer/paged/cache.rs	94.06% <100.00%> (ø)
runtime/src/utils/buffer/paged/mod.rs	97.02% <100.00%> (+0.04%)	⬆️
runtime/src/utils/buffer/paged/append.rs	97.46% <98.07%> (+0.31%)	⬆️

... and 6 files with indirect coverage changes

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[roberto-bayardo]

have added this extension of the fix to my PR (plus some other stuff).