fix(xhs): format public MCP search and detail responses

[rudycelekli]

Problem

The documented mcporter call ... | agent-reach format xhs pipeline drops real xiaohongshu-mcp output. Its public Go structs serialize search as feeds with noteCard, displayTitle, xsecToken and other camelCase fields. The formatter recognizes only older items / snake_case data and outputs {}. Detail responses additionally put note and comments.list inside a data envelope.

Changes

• Recognize search and HTTP/detail envelopes, retaining empty search results as [].
• Normalize known MCP camelCase fields to the existing compact snake_case output.
• Preserve the feed-level note ID and explicit token when note content is nested; keep inner canonical values authoritative.
• Retain useful cover/detail image URLs and sibling comments while continuing to discard structural noise.

This only formats caller-provided JSON. It adds no network calls or authentication behavior.

Evidence

Public upstream response envelopes, feed/detail/comment structs, and MCP serialization. This completes the formatter contract introduced for #134; it does not restore the obsolete read/search wrappers.

Validation

• Before: 9 regression failures and 1 compatibility control pass, including native formatter CLI invocations on upstream-shaped JSON.
• After: 18 focused formatter tests pass; all 617 repository tests pass.
• Ruff: all source and test checks pass; diff whitespace check is clean.
• Formatting: the untouched base already fails ruff format --check in 54 files; this patch follows existing local formatting and does not reformat unrelated code.
• mypy: the same 3 pre-existing diagnostics in integrations/mcp_server.py with the supplied MCP SDK 2.2 runtime; no new errors.

AI assistance: implementation and regression investigation prepared with Codex and reviewed before submission.