optimization: reduce snapshot creation time

[blindchaser]

Describe your changes and provide context

Implement pipeline-based parallel writing to significantly improve snapshot rewrite performance.

• Prefech files into page cache before snapshot creation
• Pipeline parallel writes: Decouple traversal and I/O via 3 background workers
• Large IO/channel buffer: 10k → 500k to reduce blocking and syscalls
• Priority EVM strategy: Write largest tree first to avoid I/O contention
• Skip too frequent snapshot during catch-up state

Testing performed to validate your change

• On a 250GB RAM machine with 250 MiB/s GT3 disk, snapshot creation time reduced from >3 hours to ~20 minutes.

[github-actions[bot]]

The latest Buf updates on your PR. Results from workflow Buf / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Nov 18, 2025, 10:47 AM

[codecov[bot]]

Codecov Report

:x: Patch coverage is 66.36971% with 151 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 43.72%. Comparing base (cfd70df) to head (52cb9f8). :warning: Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
sei-db/sc/memiavl/snapshot.go	66.51%	65 Missing and 8 partials :warning:
sei-db/sc/memiavl/db.go	59.52%	43 Missing and 8 partials :warning:
app/app.go	10.00%	6 Missing and 3 partials :warning:
sei-db/sc/memiavl/import.go	70.00%	7 Missing and 2 partials :warning:
sei-db/sc/memiavl/multitree.go	92.59%	2 Missing and 2 partials :warning:
sei-cosmos/baseapp/baseapp.go	0.00%	3 Missing :warning:
sei-db/config/config.go	0.00%	1 Missing :warning:
sei-db/sc/store.go	0.00%	1 Missing :warning:

:x: Your patch status has failed because the patch coverage (66.36%) is below the target coverage (70.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2537      +/-   ##
==========================================
+ Coverage   42.51%   43.72%   +1.20%     
==========================================
  Files        1271     1626     +355     
  Lines      104353   139858   +35505     
==========================================
+ Hits        44370    61148   +16778     
- Misses      56070    73177   +17107     
- Partials     3913     5533    +1620     

Flag	Coverage Δ
sei-chain	44.36% <30.76%> (-0.01%)	:arrow_down:
sei-cosmos	40.98% <0.00%> (+<0.01%)	:arrow_up:
sei-db	44.83% <67.89%> (+1.53%)	:arrow_up:
sei-tendermint	47.00% <ø> (?)
sei-wasmd	42.74% <ø> (+0.01%)	:arrow_up:
sei-wasmvm	39.65% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
app/seidb.go	82.69% <100.00%> (+0.33%)	:arrow_up:
app/test_helpers.go	31.56% <100.00%> (+0.07%)	:arrow_up:
sei-db/sc/memiavl/opts.go	100.00% <100.00%> (ø)
sei-db/ss/pebbledb/iterator.go	54.20% <100.00%> (ø)
sei-db/config/config.go	0.00% <0.00%> (ø)
sei-db/sc/store.go	0.00% <0.00%> (ø)
sei-cosmos/baseapp/baseapp.go	65.16% <0.00%> (-0.12%)	:arrow_down:
sei-db/sc/memiavl/multitree.go	78.92% <92.59%> (+2.26%)	:arrow_up:
app/app.go	73.01% <10.00%> (-0.23%)	:arrow_down:
sei-db/sc/memiavl/import.go	72.72% <70.00%> (+0.75%)	:arrow_up:
... and 2 more

... and 361 files with indirect coverage changes

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