[runtime] Model atomic blob crash recovery

[patrick-ogrady]

Summary

Adds two complementary bounded crash oracles above the production and unit-test layers:

• model_tests.rs exhausts semantic publication and recovery histories, including three-generation slot reuse and overlapping successor groups.
• scheduled_tests.rs drives the production encoder and recovery path with exact operation identities, retained-write masks, and independent recovery orders.

This is layer 5 of 6 in the atomic blob stack. It changes no production behavior and keeps model failures separate from the broader behavioral suite in #4491.

Review focus

• Every accepted state is derived from a complete predecessor or candidate vector; the model never invents or contracts a ring.
• Prepared-ring durability, hidden cleanup debt, rejected-slot consumption, and generation reuse are exercised as explicit state transitions.
• Open-first and scan-first recovery evidence is derived independently before either path can repair the backing.

Diff size

• Production code: +0 / -0 LOC
• Tests and test infrastructure: +3220 / -0 LOC
• Total: +3220 / -0 LOC

Counts are physical diff lines, including comments and blank lines. Test-only files, hooks, and lines inside #[cfg(test)] modules are counted as tests; everything else is counted as production code.

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[github-actions]

Benchmark results

Regressions: 0.

✅ `qmdb::merkleize/v=any::unordered::fixed::mmr k=10000 ch=false s=true cc=true` (2/2 gates passed)

Field	Value
Package	commonware-storage
Benchmark target	qmdb_gungraun
Variant	qmdb::merkleize/v=any::unordered::fixed::mmr k=10000 ch=false s=true cc=true
Filter	*::bench_merkleize::any_unordered_fixed_mmr
Baseline suite	commonware-storage
Gates	EstimatedCycles should decrease; tolerance 10.00%; blob_reads should decrease; tolerance 10.00%
Cargo flags	--features test-traits

Metric	Baseline	Current	Delta	Gate
Ir	13,159,318	13,119,853	-0.30%	-
L1hits	16,819,414	16,757,707	-0.37%	-
LLhits	94,113	98,841	+5.02%	-
RamHits	11,467	11,006	-4.02%	-
TotalRW	16,924,994	16,867,554	-0.34%	-
EstimatedCycles	17,691,324	17,637,122	-0.31%	EstimatedCycles should decrease; tolerance 10.00%
blob_reads	158	158	+0.00%	blob_reads should decrease; tolerance 10.00%

✅ `qmdb::merkleize/v=current::ordered::fixed::mmb chunk=256 k=10000 ch=false s=true cc=true` (2/2 gates passed)

Field	Value
Package	commonware-storage
Benchmark target	qmdb_gungraun
Variant	qmdb::merkleize/v=current::ordered::fixed::mmb chunk=256 k=10000 ch=false s=true cc=true
Filter	*::bench_merkleize::current_ordered_fixed_mmb_chunk_256
Baseline suite	commonware-storage
Gates	EstimatedCycles should decrease; tolerance 10.00%; blob_reads should decrease; tolerance 10.00%
Cargo flags	--features test-traits

Metric	Baseline	Current	Delta	Gate
Ir	15,488,996	15,434,827	-0.35%	-
L1hits	20,313,311	20,242,194	-0.35%	-
LLhits	132,020	137,611	+4.23%	-
RamHits	17,946	17,455	-2.74%	-
TotalRW	20,463,277	20,397,260	-0.32%	-
EstimatedCycles	21,601,521	21,541,174	-0.28%	EstimatedCycles should decrease; tolerance 10.00%
blob_reads	235	235	+0.00%	blob_reads should decrease; tolerance 10.00%

Baseline commit(s): f04a442f1c3c

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.54%. Comparing base (d826af2) to head (e66b230).

@@                     Coverage Diff                     @@
##           atomic-blobs-unit-tests    #4492      +/-   ##
===========================================================
- Coverage                    95.54%   95.54%   -0.01%     
===========================================================
  Files                          609      609              
  Lines                       280523   280523              
  Branches                      6944     6944              
===========================================================
- Hits                        268038   268035       -3     
- Misses                       10228    10233       +5     
+ Partials                      2257     2255       -2     

Files with missing lines	Coverage Δ
runtime/src/atomic.rs	97.35% <ø> (ø)

... and 11 files with indirect coverage changes

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