feat: Phase 5b: Add ledger/peer/tx spans + expand Grafana dashboards

[pratikmankawde]

PR Chain: #6436 → #6437 → #6438 → #6424 → #6425 → #6426 → #6427 → #6433 (this PR) / #6439 → #6493 → #6494 → #6513
Base: pratik/otel-phase5-docs-deployment

High Level Overview of Change

Add 6 new OpenTelemetry spans to instrument ledger building, ledger validation,
ledger storage, transaction application, and peer proposal/validation message
receipt. Expand all Grafana dashboards from 4 to 8 panels each and add 2 new
dashboards (Ledger Operations, Peer Network), bringing the total to 32 panels
across 5 dashboards. Each panel now includes a description explaining what it
shows and how the PromQL query calculates the metric.

Context of Change

Phase 5a (the base branch `pratik/otel-phase5-docs-deployment`) delivered
consensus spans, the observability stack (otel-collector, Jaeger, Tempo, Prometheus,
Grafana), and integration tests. During review, we identified that the
`trace_ledger` config category existed with its `XRPL_TRACE_LEDGER` macro but
had zero spans using it, and `trace_peer` had only 1 span (`tx.receive`).
Dashboard panels were limited to 4 per dashboard with no panel descriptions.

This PR fills those gaps:

New spans (6, bringing total from 10 to 16):

Span	File	Category	Key Attributes
`ledger.build`	BuildLedger.cpp:31	`trace_ledger`	`xrpl.ledger.seq`
`ledger.validate`	LedgerMaster.cpp:915	`trace_ledger`	`xrpl.ledger.seq`, `xrpl.ledger.validations`
`ledger.store`	LedgerMaster.cpp:409	`trace_ledger`	`xrpl.ledger.seq`
`tx.apply`	BuildLedger.cpp:88	`trace_transactions`	`xrpl.ledger.tx_count`, `xrpl.ledger.tx_failed`
`peer.proposal.receive`	PeerImp.cpp:1667	`trace_peer`	`xrpl.peer.id`, `xrpl.peer.proposal.trusted`
`peer.validation.receive`	PeerImp.cpp:2264	`trace_peer`	`xrpl.peer.id`, `xrpl.peer.validation.trusted`

Dashboard changes (12 → 32 panels):

• RPC Performance: 4 → 8 panels (+ throughput, success/error, top commands, WebSocket)
• Transaction Overview: 4 → 8 panels (+ heatmap, tx.apply duration, peer receive, failed rate)
• Consensus Health: 4 → 8 panels (+ mode tracking, accept vs close, validation vs close, heatmap)
• Ledger Operations: NEW, 8 panels (build/validate/store rates and durations)
• Peer Network: NEW, 4 panels (proposal/validation receive, trusted vs untrusted)

All traces viewable in both Jaeger and Grafana Tempo via OTel Collector fan-out.

Type of Change

• New feature (non-breaking change which adds functionality)
• Tests (you added tests for code that already exists, or your new feature included in this PR)
• Documentation update

API Impact

None. This change only adds internal observability instrumentation (OpenTelemetry
spans) and Docker-based Grafana dashboards. No public API, libxrpl, or peer
protocol changes.

Test Plan

Integration test (`bash docker/telemetry/integration-test.sh`) passes 24/24
with all 16 span types verified across a 6-node consensus network:

• Phase 2 (RPC): `rpc.request`, `rpc.process`, `rpc.command.*` — 5 traces each
• Phase 3 (TX): `tx.process`, `tx.receive`, `tx.apply` — 5 traces each
• Phase 4 (Consensus): `consensus.proposal.send`, `consensus.ledger_close`, `consensus.accept`, `consensus.validation.send` — 5 traces each
• Phase 5 (Ledger): `ledger.build`, `ledger.validate`, `ledger.store` — 5 traces each
• Phase 5 (Peer): `peer.proposal.receive`, `peer.validation.receive` — 5 traces each
• Spanmetrics: 22 Prometheus series with duration histograms
• Grafana: healthy with 5 dashboards, 32 panels

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.3%. Comparing base (0fc3f6b) to head (f0d8ed2).

Additional details and impacted files

@@                         Coverage Diff                          @@
##           pratik/otel-phase5-docs-deployment   #6433     +/-   ##
====================================================================
- Coverage                                81.3%   81.3%   -0.0%     
====================================================================
  Files                                    1000    1000             
  Lines                                   74764   74764             
  Branches                                 7631    7644     +13     
====================================================================
- Hits                                    60779   60771      -8     
- Misses                                  13985   13993      +8     

Files with missing lines	Coverage Δ
src/xrpld/app/ledger/detail/BuildLedger.cpp	92.4% <ø> (ø)
src/xrpld/app/ledger/detail/LedgerMaster.cpp	42.6% <ø> (ø)
src/xrpld/overlay/detail/PeerImp.cpp	5.7% <ø> (ø)

... and 8 files with indirect coverage changes

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[github-actions]

This PR has conflicts, please resolve them in order for the PR to be reviewed.

[pratikmankawde]

Phase 5b content has been absorbed into Phase 6 (#6439) during the rebase of the PR chain onto the updated Phase 3 base. All spans (ledger.build, tx.apply, ledger.store, ledger.validate, peer.proposal.receive, peer.validation.receive), dashboards (ledger-operations, peer-network), TESTING.md updates, and codecov exclusions are now part of the Phase 6 commit. Closing as merged-by-absorption.