#538 Hide Alexandria capability prices by default; add includeCosts to find_tools

Agents no longer see per-capability credit prices in Alexandria output unless they ask for them.

Default output (no prices)

• firecrawl_find_tools: drops creditsCost, perRecord, billing, recordsPerUnit and zeroDataRetentionCreditsCost from tool items and relatedTools, along with the call's own zero creditsCost.
• firecrawl_search and URL-mode firecrawl_scrape: the same fields are dropped from data.tools / tools.
• firecrawl_scrape in Alexandria mode: each result entry no longer echoes its own creditsCost. The request total data.creditsCost and receipts stay as they are.

Opt-in

• New includeCosts boolean on firecrawl_find_tools ("Include per-capability credit prices (creditsCost, perRecord) in tool results."). When it's set, output matches what it was before this change. The MCP server handles the flag itself and doesn't send it upstream; the nextTool arguments carry it forward so pagination keeps prices visible.

Copy

• The hosted instructions and the Alexandria-mode scrape copy now say execution is billed per capability and point to includeCosts for prices, replacing the "billed at the capability's listed price" wording. The README is updated to match.

Tests cover default stripping for find_tools, search and execution results, plus includeCosts passthrough and carry-forward. Contract snapshots were regenerated.

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Summary by cubic

Agents no longer see per-capability credit prices in Alexandria output unless they ask for them.

• Strips creditsCost, perRecord, billing, recordsPerUnit, and zeroDataRetentionCreditsCost from firecrawl_find_tools, firecrawl_search, and Alexandria-mode firecrawl_scrape results; request totals are unchanged.
• Adds includeCosts to firecrawl_find_tools to opt back in; the flag is handled locally and carried through pagination.
• Updates hosted instructions and README copy to describe per-capability billing and point to includeCosts.
• Releases 3.30.1 with version bumps and a changelog entry.