[Coder8124]

Old checkpoints sat flat in their project directory, and anything without a host_session landed in one `_unattached` pile. `logos migrate sessions` now moves every one of them into a conversation folder.

• Recovering the conversation. A checkpoint with no host_session is matched to its conversation through Logos's own receipt in the Claude Code or Codex transcript on this machine. Only the first line of a Logos tool result counts, and it must fall within 10 minutes of the checkpoint. Every receipt wording since 0.4 is read. A single match writes host_session into the frontmatter, so the vault stays truth. Two matches are reported as ambiguous. No match gives the checkpoint a folder of its own.
• Naming. Conversation folders are now `--`, and existing bare-id folders are renamed. `FolderID` reads the id back, so resuming by id is unchanged.
• Safety.
  • The old mtime is kept.
  • Sync copies move with their checkpoint.
  • Folder choice is locked against the Stop hook writing at the same time.
  • An unreadable transcript is skipped and named in the output.
  • Transcripts are read only when some checkpoint needs them.
  • `--dry-run` reports without moving anything.

On a copy of a real vault: 296 moved, 228 matched by receipt, 68 filed on their own, 7 folders named, 0 failed. A rerun moves 0 in 0.04s. After `logos index`, doctor reports 0 failed.

Known and not fixed: a resumed or forked Claude session repeats the earlier conversation's receipts, so those checkpoints are reported as ambiguous instead of guessed.