chore(proof): add nitro host debug logs

[jackchuma]

What changed? Why?

Adds targeted Nitro host and witness logs for debugging zeronet proof failures:

• Include L1 head metadata on Nitro proof start, failure, and success logs.
• Include L1 head metadata when host proof generation starts.
• Log the L1 provider head before witness capture, with a warning when the provider is behind the requested L1 head.
• Log raw L1 header source and length when header RLP is suspiciously short or fails to decode.
• Log oracle and hint-router channel close IO errors before exiting those loops.

This should help distinguish RPC lag, malformed debug_getRawHeader responses, prefetch-cache issues, and expected channel shutdowns.

Notes to reviewers

Logging-only change. Existing proof, witness, retry, and error-return behavior is unchanged.

How has it been tested?

• cargo fmt --package base-proof-host --package base-proof-tee-nitro-host
• cargo check -p base-proof-host -p base-proof-tee-nitro-host

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1

[github-actions]

Review Summary

Logging-only change — no behavioral or control-flow modifications. The additions are well-structured: tracing fields use proper key=value format, log levels are appropriate (warn for lag/suspicious data, error for decode failures, info for nominal state), and saturating_sub is correctly used for the lag calculation.

No issues found.

[github-actions]

✅ base-std fork tests: all 616 passed

base/base is fully in sync with the base-std spec.

Dependency	Ref	Commit
base-std	main	d4b531cd
base-anvil	0092692587d8d064dd2c6923ce26a682c58f3694	00926925