Step 4: Unify seenBlock and latestSyncData.Block into a chain-wide tracker

[Tomelia1999]

Summary

Collapses two parallel "latest block on chain" stores into one chain-wide ChainState.latestBlock:

• Per-user seenBlock (ristretto cache, 5-min TTL, keyed by dappId__consumerIp) — gone.
• Per-chain latestSyncData.Block (no TTL, in ProviderOptimizer) — gone.

Sample-fresh sync scoring (providerData.SyncBlock field deleted; outlier samples drop ALL scoring), atomic SetLatestBlock returning (block, time, advanced), race-window detection between IsOutlier and SetLatestBlock, pathological-value guard. WS subscription update lifted out of the per-dappKey fan-out loop. sharedStateId collapses to a chain-wide cache key (mixed-version compat preserved). Phase A/B/C/D + 7 Prometheus observability metrics + tier-A chaos test harness.

Docs

• Design doc: protocol/rpcconsumer/docs/consumer-latestblock-managment/unify-seenBlock-latestSyncData.md (12 formal decisions in §11, implementation task list in §14)
• Demo scenarios: protocol/rpcconsumer/docs/consumer-latestblock-managment/testing-process/unification-demo-scenarios.md
• Env setup + validation: protocol/rpcconsumer/docs/consumer-latestblock-managment/testing-process/unification-demo-env-setup.md (§8 covers the 7 Prometheus metrics)
• Chaos test harness: scripts/test/chaos/tier_a_poisoning/
• Progress: protocol/rpcconsumer/docs/probing/improvements-proposals/fixes-progress.md (Step 4)

Test plan

• `go test ./protocol/... ./ecosystem/cache/...` green
• Live validation against local Lava + 3 providers + cache + 2 consumers (scenarios A2, B1, B2, C3, D2, E1 — see env setup doc)
• 7 Prometheus metrics confirmed live (M1–M7)
• Tier-A chaos suite shipped (5 poisoning scenarios + smoke + run-all)

Stacked PR

Depends on #2297 (Steps 1+2) and #2298 (Step 3). Targets `step-3-sync-score-from-probes`.

🤖 Generated with Claude Code

[github-actions]

Hey there and thank you for opening this pull request! 👋🏼

We require pull request titles to follow the Conventional Commits specification and it looks like your proposed title needs to be adjusted.

Details:

No release type found in pull request title "Step 4: Unify seenBlock and latestSyncData.Block into a chain-wide tracker". Add a prefix to indicate what kind of release this pull request corresponds to. For reference, see https://www.conventionalcommits.org/

Available types:
 - feat: A new feature
 - fix: A bug fix
 - docs: Documentation only changes
 - style: Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc)
 - refactor: A code change that neither fixes a bug nor adds a feature
 - perf: A code change that improves performance
 - test: Adding missing tests or correcting existing tests
 - build: Changes that affect the build system or external dependencies (example scopes: gulp, broccoli, npm)
 - ci: Changes to our CI configuration files and scripts (example scopes: Travis, Circle, BrowserStack, SauceLabs)
 - chore: Other changes that don't modify src or test files
 - revert: Reverts a previous commit