docs: align Alexandria discovery and terms with the beta CLI

[developersdigest]

Alexandria's docs now match the published beta CLI and the provider-terms API: agents can browse the live catalogue, inspect a selected contract, and read or explicitly accept the exact agreement for their authenticated organization.

Changes

• Use npx firecrawl-cli@alexandria, progressive category/provider/tool browsing, find-tools --options, and scrape --alexandria in the setup and execution examples.
• Document live provider and capability IDs, natural-language Find Tools queries, and the difference between item navigation and page pagination. Groups are optional.
• Add the beta.14 terms flow: alexandria terms show, then explicit acceptance with --terms-version, --digest, and --confirm. Document GET /exchange/provider-terms, POST /exchange/provider-terms/accept, the success receipt, changed agreements, and uncertain outcomes.
• Explain setup of the Alexandria skill and the separate charge for web search. Remove references to absent search-result example fields.
• Keep MCP availability release-qualified: inspect the connected server's tool inventory, including terms tools, before using it.

Validation

• Confirmed the npm alexandria tag is 1.23.4-alexandria-beta.14 and checked its published terms acceptance help.
• Checked the terms request/response contract against merged Firecrawl #4668.
• Earlier live validation covered CLI discovery, compact tool listings, selected contracts, and zero-credit catalogue receipts. No real agreement was accepted for this update.
• Locale check selftest, extraction-hostile markdown check, and git diff --check pass.
• The locale literals check still reports the same 14 existing violations as the previous CI run.
• Mintlify validation on Node 22 reports 17 missing-snippet warnings in unchanged Fire-1 and SDK pages; strict validation exits nonzero. No warning names either edited page.

Stacked on #1404, targeting feat/exchange. MCP implementation is tracked separately in #405.