feat(import): add basou import claude-code for native transcripts

[takashi-matsuyama]

What

Adds basou import claude-code: derive Basou sessions from Claude Code's
native transcripts (~/.claude/projects/<encoded-cwd>/*.jsonl) after the
fact, rather than wrapping a live process with basou run.

Sessions produced in any Claude Code surface — desktop app, IDE, or CLI —
write the same native transcript to disk, so this lets them be captured for
provenance without changing how the tool is launched.

How

• A pure transform (transcript-importer.ts) maps a transcript's
  message-level records to Basou's provenance events, then hands the result
  to the existing importSessionFromJson pipeline — id minting, path
  sanitization and schema validation are reused unchanged.
• MVP derives: session_started / session_ended, command_executed (from
  Bash tool uses, recorded as bash -c "<line>"), and file_changed (from
  Edit / Write / NotebookEdit). Events are sorted by occurred_at
  because transcripts are not timestamp-ordered on disk.
• Adds the additive claude-code-import session source.kind.
• Flags: --all, --session <id>, --project <path>, --dry-run, --json.
• Transcripts with no observable command / file action are skipped.

Out of scope (future)

Approval / decision / task derivation, and other vendors' native logs.

Tests

• Unit tests for the transform: lifecycle bounds, command/file mapping,
  ordering of unsorted records, skip-empty, malformed-record tolerance.
• Integration tests for the CLI: import, dry-run, single session, skip,
  and error paths.
• typecheck / build / full test suite / lint all green.

🤖 Generated with Claude Code