Add docs/cli.md — public CLI reference

[pimfeltkamp]

Summary

Adds `docs/cli.md` as the single public doc covering the `cryptohopper` CLI. Pairs with `docs/sdks.md` (PR #3).

What it covers

• Install: npm + platform-specific binary URLs + SHA256 verification
• Authentication: browser flow, `--token` fallback, env overrides
• Every subcommand with usage example
• Confirmation gates (`--yes`) on destructive commands, including the 0.5.1 security fix documentation
• Exit code table (stable contract across releases)
• `--json` output contract
• Upgrade command requirements (compiled binary only, not `node dist/index.js`)

Test plan

• Render on GitHub; confirm the TOC flows
• Verify every install command is accurate against the current release
• Confirm the commands list matches src/index.ts (it does — sourced from the file directly)

[pimfeltkamp]

Pushed a small follow-up commit that strikes ### Market data (public, no auth) from the heading and adds a 1-line clarification about why these are 'public' data but still need auth — same false-claim cleanup that just landed across the SDK READMEs and wikis from resources#9. Two-line README diff. No re-review beyond a skim.