Enrich JSON Session Summary Export · Entire

Summary

All four specs implemented, formatted, linted clean, and tested.

Spec 1 — Full summary in --json (explain_export.go)

• Extended checkpointSessionSummary with Learnings, Friction, OpenItems (matching upstream tags learnings/friction/open_items, all omitempty). Added nested checkpointSessionLearnings (repo/code/workflow, omitempty) and reused checkpoint.CodeLearning for code entries.
• New summaryToExportJSON helper populates them from meta.Summary, reusing the existing hasAnyLearning helper so an empty learnings block stays nil (no {} noise). Redaction is already applied upstream, so no new privacy surface.

Spec 2 — Prose-list truncation visibility (explain.go)

• runExplainBranchWithFilter now probes branchCheckpointsLimit+1, slices to the cap, and prints a stderr note when checkpoints are hidden. Logic extracted into testable capBranchCheckpoints. Note wording is honest — "showing first 100 checkpoints (more exist); rerun with --json --limit for more", never an exact remaining count. Threaded errW through the call chain.

Spec 3 — Fast-fail --generate on imported (explain.go)

• Added a metadata-only checkpoint.ReadCheckpoint guard before loadCheckpointForExplain, so imported checkpoints are rejected before any transcript-blob fetch. Removed the now-redundant post-load guard.

Spec 4 — Clearer no-trailer message (explain.go)

• Hint now reads "the commit exists but was not created during an Entire session (or its trailer was removed)", distinguishing a found-but-untracked commit from "commit not found".

Tests

• TestSessionMetadataToJSON_FullSummary + TestSessionMetadataToJSON_EmptySummaryStaysClean (Spec 1)
• TestCapBranchCheckpoints with under/at/over-cap subtests (Spec 2)
• Added a --generate-on-imported rejection assertion to the existing TestImportClaudeCode_EndToEnd integration test (Spec 3)
• Spec 4 needed none (existing tests only assert the title, which is unchanged).