Execution graph substrate: SessionRelationshipRecord + ToolResultEventRecord (#42)

[willwashburn]

Refs #42.

This is a tractable first PR for the cross-source execution graph called for in #42. The issue calls out that several backlog items (subagent tree #8, waste-pattern detection #11, future archive work) implicitly assume normalized session relationships and tool-result chronology that today's TurnRecord is too lossy to carry. Rather than try to ship every source / consumer at once, this PR lays the foundation:

What landed

@relayburn/reader — two new record shapes (additive, v: 1):

• SessionRelationshipRecord — relationshipType: 'root' | 'continuation' | 'fork' | 'subagent', plus parentToolUseId / agentId / subagentType / description for subagent edges. The schema covers all four relationship kinds the issue spells out; only root and subagent are populated in this PR (Claude historical logs don't surface fork / continuation evidence we don't already cover).
• ToolResultEventRecord — chronological tool-output stream keyed by toolUseId and a per-session monotonic eventIndex. Status: running / completed / errored / cancelled / unknown. Discriminator eventSource covers tool_result / subagent_notification / queue_event / progress_event / function_call_output. Metadata-only — contentLength + contentHash, never raw bytes.

Claude passive reader (parseClaudeSession + parseClaudeSessionIncremental) now returns relationships and toolResultEvents alongside the existing turns / content / events arrays. Roots emit once per session id; one subagent row per distinct invocation discovered (joining Subagent.agentId); each tool_result block becomes a ToolResultEventRecord. Agent/Task spawn events are post-annotated with the resolved subagent's agentId so the two record types can be joined. The incremental parser respects the same endOffset deferral content/compaction events use, so resumed ingest doesn't double-emit.

@relayburn/ledger picks up two new LedgerLine kinds — relationship and tool_result_event — with matching appendRelationships / appendToolResultEvents writers, queryRelationships / queryToolResultEvents readers, and isSessionRelationshipLine / isToolResultEventLine guards. Both append-only; both dedup through the existing ~/.relayburn/ledger-index namespace via new relationshipIdHash (keyed on type + agentId + parentToolUseId) and toolResultEventIdHash (keyed on sessionId + toolUseId + eventIndex). rebuildIndex re-indexes both kinds.

@relayburn/cli — burn ingest (runtime + hook paths) and burn claude now persist relationships + tool-result events when the Claude reader emits them. No new flags or output yet.

What's deferred

• Codex passive-reader population — function_call_output, spawn_agent / wait relationships, terminal subagent notifications. The shape is in place; codex.ts wiring is a follow-up.
• OpenCode passive-reader population — parent session ids, tool-result sizes / statuses where exposed.
• Hook-path ingest (#7) emitting the same shapes — current Claude hook ingest goes through the reader, so it picks up everything the reader emits, but a future hook-only event source (e.g. subagent_notification) needs its own emitter.
• Consumer CLI surface — burn summary --subagent-tree, burn diagnose, burn waste --patterns, burn summary --by-relationship. The execution graph is now persisted, so these can be built on top.
• Fork / continuation row population for Claude. Historical Claude logs surface parentUuid chains we already use for subagents; explicit fork/continuation evidence (across-file sourceSessionId, /resume markers) needs targeted parser work.

Test plan

• pnpm install && pnpm run test:ts — 347 tests pass (added 8 new tests).
• Reader: tool-result events emit with monotonic eventIndex, the right status / isError / contentLength / contentHash for the retry-loop fixture.
• Reader: nested-subagent fixture yields one root + two subagent relationship rows with correct agentId / parentToolUseId / relatedSessionId / subagentType / description, and the Agent/Task spawn tool_result events get joined back to the right child invocation via agentId.
• Ledger: round-trip appendRelationships / queryRelationships and appendToolResultEvents / queryToolResultEvents; dedup is keyed correctly so re-appending the same record doesn't grow the file; query filters work for sessionId (matching child or parent) and source.
• Ledger: rebuildIndex re-indexes the new line kinds and re-appending after rebuild is a no-op.

🤖 Generated with Claude Code

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[devin-ai-integration]

Devin Review found 1 potential issue.

⚠️ 1 issue in files not directly in the diff

⚠️ Root CHANGELOG.md missing [Unreleased] entry for cross-package work (AGENTS.md violation) (CHANGELOG.md:7)

This PR touches three packages (packages/reader, packages/ledger, packages/cli) and each package's CHANGELOG.md is updated under [Unreleased]. However, the root CHANGELOG.md has no corresponding entry. AGENTS.md states: "Update [Unreleased] only when the work spans packages or warrants a top-level summary; single-package work belongs only in that package's CHANGELOG." This PR clearly spans packages, so the root CHANGELOG should have an [Unreleased] entry describing the execution-graph substrate addition, consistent with how the existing MCP entry (CHANGELOG.md:11) was added for its cross-package work.

View 5 additional findings in Devin Review.

[willwashburn]

Re: Devin review — root CHANGELOG.md missing [Unreleased] entry for cross-package work.

Fixed in e0ee4f1. Added an [Unreleased] bullet to the root CHANGELOG.md summarizing the execution-graph substrate, mirroring the shape of the existing MCP entry one bullet up (top-level summary + indented per-package bullets for reader / ledger / cli). Per AGENTS.md line 38, this PR qualifies because it spans three packages.

The other 5 findings only render on Devin's site and were not posted as line-anchored review comments here, so I can't address them through GitHub. If any are blockers, please re-post them as inline review comments.