fix(x/audit): bridge cascade_kademlia_db_bytes from HostReport to SupernodeMetricsState

[mateeullahmalik]

Summary

Bridges cascade_kademlia_db_bytes from the audit HostReport (per-epoch) into x/supernode SupernodeMetricsState, which is the sole source Everlight payout and eligibility queries read from post LEP-6 §12.

Without this fix, Everlight distributes zero ulume to anyone on master and 1.12.0 today — confirmed live on devnet. See "Why this is needed" below.

Why this is needed

LEP-6 §12 (PR #122, 2026-04-28):

• Removed cascade_kademlia_db_bytes (field 6) from audit.HostReport
• Rewrote x/supernode/v1/keeper/audit_metrics.go::getLatestCascadeBytesFromAudit to read from SupernodeMetricsState instead of from audit epoch reports

But the migration was half-completed: no chain-side writer was added to populate SupernodeMetricsState.CascadeKademliaDbBytes from the audit-submission path. The only remaining writer is the now-operationally-dead legacy MsgReportSupernodeMetrics handler — and supernode@master / v2.5.0-rc has explicitly disabled the legacy reporter (supernode/cmd/start.go:29: "Legacy supernode metrics reporter has been superseded by epoch-scoped audit reporting in x/audit").

Result on chain 1.12.0 / master today:

1. SuperNode submits epoch report — but post-LEP-6 §12, the audit module doesn't persist cascade_kademlia_db_bytes anywhere
2. Every payment-period boundary, distributePool iterates all ACTIVE/STORAGE_FULL SNs, calls getLatestCascadeBytesFromAudit → returns found=false for every SN
3. candidates slice is empty → no SN receives any payout
4. QuerySNEligibility returns Eligible: false, Reason: "audit report is stale" for every SN

This PR closes the gap by making the audit SubmitEpochReport handler the single, sole writer of SupernodeMetricsState.CascadeKademliaDbBytes, in line with the post-LEP-6 design intent ("only audit-module epoch reports are valid").

Behavior change

Before	After
audit.HostReport has no cascade_kademlia_db_bytes field	audit.HostReport.cascade_kademlia_db_bytes (field 6, double) restored as a metric-courier
Audit-side consensus logic consumes cascade_kademlia_db_bytes	Unchanged — still does not consume it (LEP-6 §12 intent preserved)
SupernodeMetricsState.CascadeKademliaDbBytes only written by legacy MsgReportSupernodeMetrics (now dead)	Written by audit's SubmitEpochReport handler after a successful epoch report is persisted
Everlight payouts: 0 ulume to anyone	Everlight payouts: proportional to SN-reported cascade DB bytes

Invariant table

#	Field / Behavior	Contract	Enforcement Point	Test Coverage
I1	HostReport.cascade_kademlia_db_bytes	Finite, ≥ 0; zero valid	validateHostMetricFields in msg_submit_epoch_report.go	1 happy positive, 1 zero, 4 violation (NaN, +Inf, -Inf, negative)
I2	Audit SubmitEpochReport is the SOLE writer of SupernodeMetricsState.CascadeKademliaDbBytes post-LEP-6 §12	After successful epoch report, upsert with correct val addr, current block height, incremented ReportCount	bridgeCascadeBytesToSupernodeMetrics	happy-path persistence with field-by-field assertions
I3	Bridge preserves prior non-cascade SupernodeMetrics.* fields	Read-modify-write	same	dedicated preservation test seeds non-cascade fields → submits → asserts preserved
I4	Read path (getLatestCascadeBytesFromAudit, distribution.go, query_get_reward_eligibility.go) unchanged	No code change	n/a	existing tests still pass

Bridge defensively no-ops with an audit_cascade_bytes_bridge_skipped event if the SuperNode record has an empty/invalid ValidatorAddress (a pre-existing x/supernode invariant violation outside audit's scope).

Files

File	Change
proto/lumera/audit/v1/audit.proto	+9 — restore cascade_kademlia_db_bytes = 6 with metric-courier comment
x/audit/v1/types/audit.pb.go	regenerated
x/audit/v1/types/errors.go	+1 — ErrInvalidHostMetric (code 18)
x/audit/v1/keeper/msg_submit_epoch_report.go	+90/-2 — validation + bridge helper, wired into the SubmitEpochReport handler after SetReport
x/audit/v1/keeper/msg_submit_epoch_report_cascade_bytes_test.go	NEW — invariant tests (8 cases)
x/audit/v1/keeper/msg_submit_epoch_report_storagefull_test.go	+16 — GetMetricsState/SetMetricsState AnyTimes() expectations for the 2 storagefull-transition tests whose SN has a real validator address
docs/static/openapi.yml	regenerated

Risk & rollback

Risk: low.

• Proto field is purely additive (re-introducing field 6 that was previously assigned to this same field; never repurposed).
• Validation is fail-closed against malformed input (NaN/Inf/negative).
• Bridge is defensively no-op when val addr is missing.
• All existing unit + integration tests pass unchanged.

Rollback: revert this commit. Devnet/mainnet falls back to the current broken-Everlight state (no worse than today).

Migration / upgrade impact

• Proto schema additive: a new optional field on an existing message — backward-compatible at the wire level; old binaries that don't know field 6 will ignore it.
• No state migration needed: SupernodeMetricsState schema unchanged. New writers just start populating Metrics.CascadeKademliaDbBytes from the audit path going forward.
• Upgrade ordering: this PR is a prerequisite for any chain that ships supernode@v2.5.0-rc (or anything master-ish on the supernode side that emits HostReport.cascade_kademlia_db_bytes). Without this PR, those SN binaries' epoch-report Txs fail at proto decode (errUnknownField "*types.HostReport": {TagNum: 6, WireType:"fixed64"}: tx parse error).

Verification

# Unit (CI: make unit-tests)
go test ./x/audit/... ./x/supernode/...
# → ok, all green

# Integration (CI: make integration-tests, -tags=integration,test)
go test -tags=integration,test -p 4 ./tests/integration/...
# → ok, all green including tests/integration/{audit,supernode,everlight}

# Systemtests vet (Anti-pattern 13 mandate — separate Go module)
cd tests/systemtests && go vet -tags system_test ./...
# → clean

# Binary build
go build -o /tmp/lumerad ./cmd/lumera
# → ok

Observability

Two new event types:

• audit_cascade_bytes_bridge_skipped — emitted when the bridge no-ops due to empty/invalid ValidatorAddress. Attributes: module, supernode_account, validator_address (when present), reason, error (when present).

Follow-up

The legacy MsgReportSupernodeMetrics handler remains in the codec (still registered, still callable) but no SN binary sends it. Removing it cleanly requires a chain upgrade handler and is out of scope for this surgical fix — to be done as a follow-up cleanup PR.

Cherry-pick plan

After merge to master, cherry-pick onto 1.12.0 release branch via a follow-up PR.