bug: syncRegeneratedSession uploads content to LFS but discards fileRefs, creating orphan blobs

[galexy]

Symptom

ox session regenerate <name> (default mode — artifact regeneration) uploads regenerated content files to LFS, but throws away the returned file references. meta.json is never updated to point at the newly-uploaded blobs. The blobs become orphaned in LFS storage (eligible for server-side GC) and subsequent uploads still reference whatever OIDs were in the old meta.json.

Evidence

Reproduced live during #519 investigation. After regenerating session artifacts from a rebuilt raw.jsonl:

• uploadSessionLFS pushed the 235-entry raw.jsonl content to LFS and returned a fresh OID.
• meta.json was never updated to reference the fresh OID.
• The next ox session upload used the old OID from the preserved meta.json and published the stale (50-entry) version.
• The 235-entry blob remains in LFS storage with no reference anywhere. It's an orphan.

Root cause

cmd/ox/session_regenerate.go:207-223:

// syncRegeneratedSession re-uploads to LFS and pushes to the ledger for a single session.
func syncRegeneratedSession(projectRoot, sessionPath, sessionName string) error {
    if _, err := uploadSessionLFS(projectRoot, sessionPath); err != nil {
        //         ^^^
        //         fileRefs returned by uploadSessionLFS are DISCARDED
        return fmt.Errorf("LFS upload: %w", err)
    }

    ledgerPath, err := resolveLedgerPath()
    if err != nil {
        return fmt.Errorf("resolve ledger: %w", err)
    }

    if err := commitAndPushLedger(ledgerPath, sessionName); err != nil {
        return fmt.Errorf("commit and push: %w", err)
    }

    return nil
}

The return value from uploadSessionLFS is assigned to _. No meta.json update, no WritePointerFiles. commitAndPushLedger then commits whatever *.jsonl / *.md files the glob matches — which are still the un-pointerized content files — pushing full content to the ledger repo (also wrong, since LFS pointers should be what's committed).

Impact

• Orphan LFS blobs. Every ox session regenerate call leaves orphaned blobs behind. Eventually GC'd, but wastes storage and network in the meantime.
• meta.json drift. After regenerate, meta.json on disk still references old OIDs while new blobs exist in LFS. Any subsequent read that follows the pointer gets stale data.
• Bad git commits. Because pointer-replacement never runs, commitAndPushLedger commits the full content files instead of pointer stubs. The ledger git repo grows with every regenerate.
• Subsequent uploads publish wrong content. See sibling issue (ox session upload replaces files with pointers from preserved meta.json before reading them).

Fix direction

Mirror the pattern used correctly in cmd/ox/agent_session.go:1218-1252:

fileRefs, err := uploadSessionLFS(projectRoot, sessionPath)
if err != nil { ... }

// load + update meta.json
meta, err := lfs.ReadSessionMeta(sessionPath)
if err != nil { ... }
meta.Files = fileRefs
if err := lfs.WriteSessionMetaOnly(sessionPath, meta); err != nil { ... }

// commit with pointer stubs
if err := commitAndPushLedger(ledgerPath, sessionName); err != nil { ... }

// replace content with pointers AFTER successful push
if _, err := lfs.WritePointerFiles(sessionPath, meta.Files); err != nil { ... }

Alternatively, extract a shared helper that encapsulates the upload → meta.Files update → commit → post-push pointer-replacement sequence and use it from every code path that uploads (session_upload_cmd.go, session_regenerate.go, agent_session.go, daemon agentwork).

Acceptance

• After ox session regenerate <name>, meta.json references the fresh LFS blob OIDs for any content that was regenerated.
• ox session upload <name> immediately after regenerate uploads correctly (no stale content).
• No orphan blobs produced by the regenerate → upload sequence.

Related

• Sibling issue: ox session upload pre-upload pointer replacement. Same class: upload paths don't coherently update meta.json.
• Sibling issue: buildSessionMeta preserves stale entry_count. Same class.
• Discovered during bug: session recording produces empty raw.jsonl (header only, 0 turns captured) on macOS / Claude Code 2.1.112 / ox 0.6.3 #519 investigation.