fix(finality): reject PoDA-only finality

[sidhujag]

Summary

Fails closed when canonical Syscoin RPC has no record for a DA blob. PoDA check_vh remains an availability/retrieval fallback, but it can no longer establish either chainlock or confirmation finality.

Previously, an RPC miss plus any PoDA archive hit returned Finalized. Because PoDA supplies neither a chainlock nor a mined height, an unavailable, compromised, or untrusted archive could bypass the configured Bitcoin finality policy and suppress timeout republishing.

Security properties

• chainlock mode returns Missing on a canonical RPC miss, regardless of PoDA availability;
• confirmation mode returns Missing on a canonical RPC miss, regardless of PoDA availability;
• Missing remains eligible for timeout republishing;
• PoDA fallback is unchanged for blob availability and retrieval;
• all changed production logic carries explicit SYSCOIN: rationale.

Validation

• cargo +1.93.1 test --locked: 35/35 tests pass;
• cargo +1.93.1 clippy --locked --all-targets -- -D warnings: passes;
• formatting and diff checks pass.

The zkSYS V32 branch still requires the Blake2s publication behavior from v0.1.13, whereas current v0.1.14 switched publication IDs to Keccak. The same reviewed fix is therefore backported, patch-identically, on commit 23de0d4 (codex/v0.1.13-fail-closed-finality) for an exact immutable server dependency pin. This PR fixes main; a future release should carry the fix forward as well.

[sidhujag]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Can't wait for the next one!

Reviewed commit: 3556e714c6

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