feat(checkpoint): add compact_transcript path to metadata.json

[computermode]

https://entire.io/gh/entireio/cli/trails/655

What

Following PR #1510, this takes a simpler approach to surfacing the compact transcript in checkpoint metadata. Instead of repointing the root metadata.json sessions[].transcript at transcript.jsonl, the pointer keeps targeting full.jsonl and a sibling path field is added:

• sessions[].compact_transcript holds the path to transcript.jsonl when a compact transcript was generated and written into the session directory.
• The field is omitted for non-compactable, empty, or oversized transcripts and for checkpoints written by older CLI versions.

"sessions": [
  {
    "metadata": "/ab/c123def456/0/metadata.json",
    "transcript": "/ab/c123def456/0/full.jsonl",
    "compact_transcript": "/ab/c123def456/0/transcript.jsonl",
    "content_hash": "/ab/c123def456/0/content_hash.txt",
    "prompt": "/ab/c123def456/0/prompt.txt"
  }
]

This avoids the pointer-flip and the compact_transcript_start offset machinery from #1510, while giving external readers (server/UI) a direct path to the compact transcript next to full.jsonl.

How

• Added CompactTranscript string (json:"compact_transcript,omitempty") to SessionFilePaths in api/checkpoint/metadata.go, placed right after the transcript field, and corrected the Transcript doc comment (it always points at full.jsonl).
• In writeSessionToSubdirectory (persistent.go), the path is derived directly from the tree entry: set to /<sessionPath>/transcript.jsonl only when that entry exists. Deriving from the actual tree entry (rather than threading a separate signal) keeps the pointer from dangling, and follows the same write-once lifecycle as the existing transcript/content_hash pointers.
• This is the only metadata location that stores a transcript path — the session-level metadata.json carries only offsets/identifiers, not a full.jsonl path — so compact_transcript is added in exactly the one place the full.jsonl path appears.
• Updated tests to assert the path is set for a compactable transcript and absent for a non-compactable one.

Reviewer notes

• The compact transcript storage itself is unchanged: it remains scoped per-checkpoint via checkpoint_transcript_start (no full-transcript-plus-offset change from feat(checkpoint): point metadata.json at full compact transcript.jsonl #1510).
• mise run lint (0 issues) and mise run test (6709 tests pass) verified locally.

Rendered Markdown

• CLAUDE.md
• docs/architecture/sessions-and-checkpoints.md

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

Comment @cursor review or bugbot run to trigger another review on this PR

^{Reviewed by Cursor Bugbot for commit 278addd. Configure here.}

[Copilot]

Pull request overview

This PR adds an explicit, backward-compatible signal in committed checkpoint metadata indicating whether a compact transcript (transcript.jsonl) was generated for a session, while keeping sessions[].transcript pointing at the raw full.jsonl used by CLI read paths.

Changes:

• Add sessions[].has_compact_transcript (omitempty) to checkpoint summary metadata to indicate compact transcript availability.
• Set the flag during checkpoint writes by detecting the presence of transcript.jsonl in the in-memory git tree entries.
• Update docs and tests to reflect/validate the new metadata shape.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
docs/architecture/sessions-and-checkpoints.md	Updates storage/metadata documentation and JSON example to include has_compact_transcript while keeping transcript on full.jsonl.
cmd/entire/cli/checkpoint/persistent.go	Derives and records HasCompactTranscript on session file paths based on whether transcript.jsonl was written into the checkpoint tree.
cmd/entire/cli/checkpoint/persistent_compact_transcript_test.go	Extends existing compact transcript tests to assert the new has_compact_transcript behavior for compactable vs non-compactable transcripts.
CLAUDE.md	Updates strategy documentation to describe the new flag for external readers.
api/checkpoint/metadata.go	Extends the public metadata contract (SessionFilePaths) with has_compact_transcript and updates transcript field documentation accordingly.