Refresh Claude skill docs for current mcpc syntax and features (#257)

Rewrites the bundled Claude skill (`docs/claude-skill/SKILL.md`) for the
current command-first (0.3.0+) mcpc, so agents get an accurate, complete
on-ramp instead of the removed one-shot syntax. Redoes #256 as a full
content refresh rather than a syntax-only patch.

- Reframes around the connect-then-use session model; drops the
long-gone one-shot `mcpc <url> <command>` and `--config` forms and the
stale session-state list
- Adds the features agents need to get productive: config
auto-discovery, `grep` progressive tool discovery, async tasks,
OAuth/bearer/profile auth, the AI-isolation proxy, experimental skills,
and `logs`/`ping`/`clean`
- Updates `docs/examples/company-lookup.sh` to command-first
`connect`/`login`/`close`

Supersedes #256.

https://claude.ai/code/session_01K4HdwtJH2eDq8dVvhEKBam

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_Generated by [Claude
Code](https://claude.ai/code/session_01K4HdwtJH2eDq8dVvhEKBam)_

Co-authored-by: Claude <noreply@anthropic.com>