fix(node): restore layer1-verify validator startup defaults

[curryxbo]

Problem

A from-scratch layer1-verify validator panics on startup:

panic: open /opt/data/data/write-file-atomic-...: no such file or directory
  privval.(*FilePVLastSignState).Save
  privval.LoadOrGenFilePV
  main.L2NodeMain  (node/cmd/node/main.go:134)

Two behaviors regressed when PR #966 (centralized sequencer) merged the old if isValidator { ... } else { ... } split into one unified startup path:

1. LoadOrGenFilePV became unconditional. Pre-Feat: Sequencer Final PR  #966, layer1 validators ran the derivation path and never touched Tendermint priv-validator. Now every node calls it — but a layer1 validator never starts Tendermint and has no <home>/data/ dir, so LoadOrGenFilePV → Save() → write-file-atomic fails to create its temp file and panics.
2. derivation.confirmations default changed from finalized (pre-Feat: Sequencer Final PR  #966) to a fixed latest-10 depth. That's the intended default for consensus fullnodes (paired with the reorg detector), but it silently changed validator behavior.

Fix

• main.go: load the derivation config before the priv-validator step; only LoadOrGenFilePV when the node will actually start Tendermint (i.e. VerifyMode != layer1). Layer1 validators hand the executor a nil pubkey — both NewExecutor (executor.go:92-94) and the sequencer-set check tolerate nil, and a layer1 validator is correctly never matched as a sequencer.
• config.go: for VerifyMode == layer1, default Confirmations back to rpc.FinalizedBlockNumber — unless the operator explicitly set --derivation.confirmations. Consensus fullnodes keep the latest-N default and the reorg detector.

Scope / compatibility

• Only affects layer1-verify (validator) nodes. Sequencer and local-verify fullnodes are unchanged.
• Explicit --derivation.confirmations still wins.
• No new <home>/data/ requirement for validators — restores pre-Feat: Sequencer Final PR  #966 behavior.

Test

• go build ./cmd/... ./derivation/... ✅
• go vet ./derivation/ ✅

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Added Layer 1 verification support that skips unnecessary validator initialization.
  • Layer 1 verification now defaults to finalized block confirmations when no custom confirmation setting is provided.

• Bug Fixes

  • Preserved the ability to override the default confirmation behavior with an explicit configuration.

[claude]

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: ebe34bd7-eeea-46a1-b057-b6c630f0df90

📥 Commits

Reviewing files that changed from the base of the PR and between 21d05b9 and e8653e1.

📒 Files selected for processing (2)

• node/cmd/node/main.go
• node/derivation/config.go

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📝 Walkthrough

Walkthrough

Changes

Derivation and validator startup

Layer / File(s)	Summary
Layer1 confirmation default node/derivation/config.go	Layer1 verification uses rpc.FinalizedBlockNumber unless derivation confirmations were explicitly set.
Conditional validator initialization node/cmd/node/main.go	Derivation configuration loads before startup mode selection, and Tendermint private-validator loading and public-key extraction are skipped in Layer1 verify mode.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Suggested reviewers: dylancai9, fletcherman, tomatoishealthy

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: restoring layer1-verify validator startup defaults.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/validator-layer1-defaults

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