CLI: implement list, read, search, create, update, delete, validate, export, stats subcommands

[fuseraft]

docs/guide/cli.md documents these as "Additional CLI Commands Planned":

Commands for list, read, search, create, update, delete, validate, export, and stats are planned for future releases.

Today these operations are only reachable through the chat interface (compendium chat), the Web UI, the REST API, or direct file editing. Add first-class CLI subcommands so a catalog can be scripted/automated without spinning up the web server or going through the agent.

Scope:

• compendium list — list concepts (with filters: type, tag, status)
• compendium read — print a concept by id
• compendium search — search concepts by text/tag/type
• compendium create / update — non-interactive concept creation/edits
• compendium delete — remove a concept
• compendium validate — validate a bundle/concept against the OKF spec
• compendium export — export filtered concepts (JSON/CSV)
• compendium stats — bundle statistics (concept counts by type/status, staleness, etc.)

Each subcommand should mirror the semantics of its Web UI / REST API equivalent (see docs/reference/api.md) rather than introducing a divergent behavior.