harden: add layout invariant validation to detectSlabLayout

[0x-SquidSol]

Summary

• detectSlabLayout returns layouts from 10+ buildLayout*() functions with no post-construction validation
• Past layout constant errors (V1M bitmap 726→720, V_ADL bitmap 1006→1008, V12.1 HOST bitmapOff double-subtraction) were only caught by failing tests downstream — not at detection time
• Fix: validateLayout helper checks 3 structural invariants before returning:
  1. accountsOff > engineOff — accounts array lives after engine header
  2. engineBitmapOff > engineParamsOff — bitmap follows params in engine struct
  3. maxAccounts ∈ [1, 65536] — sane tier bounds
• Wraps all 11 return paths in detectSlabLayout
• Catches layout constant transcription errors immediately instead of producing garbled data downstream

Test plan

• No new test failures (729 passed, same 16 pre-existing)
• All 10+ layout variants pass all 3 invariants (verified by agent analysis)

🤖 Generated with Claude Code

[coderabbitai]

Warning

Rate limit exceeded

@0x-SquidSol has exceeded the limit for the number of commits that can be reviewed per hour. Please wait 17 minutes and 18 seconds before requesting another review.

Your organization is not enrolled in usage-based pricing. Contact your admin to enable usage-based pricing to continue reviews beyond the rate limit, or try again in 17 minutes and 18 seconds.

⌛ How to resolve this issue?

After the wait time has elapsed, a review can be triggered using the @coderabbitai review command as a PR comment. Alternatively, push new commits to this PR.

We recommend that you space out your commits to avoid hitting the rate limit.

🚦 How do rate limits work?

CodeRabbit enforces hourly rate limits for each developer per organization.

Our paid plans have higher rate limits than the trial, open-source and free plans. In all cases, we re-allow further reviews after a brief timeout.

Please see our FAQ for further information.

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: f4457292-a4c9-4062-8752-aae00fe057e1

📥 Commits

Reviewing files that changed from the base of the PR and between 2f80d79 and 5e1a90e.

📒 Files selected for processing (1)

• src/solana/slab.ts

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}