refactor(mcp): trim SERVER_INSTRUCTIONS to lean on authoritative docs (#3910)

* refactor(mcp): trim SERVER_INSTRUCTIONS to lean on authoritative docs

JMESPath and describe_tool stanzas previously inlined grammar / envelope /
quota detail that is now documented in docs/mcp-jmespath.mdx,
docs/mcp-error-catalog.mdx, and docs/mcp-tools-reference.mdx. Each
stanza collapses to one sentence stating the affordance + use case +
canonical-docs URL. Prompts and resources stanzas are unchanged.

initialize.result.instructions: 1945 B → 1397 B (-548 B / 28.2%) emitted
once per session. SERVER_VERSION 1.9.0 → 1.10.0; server-card.json synced;
version assertions in mcp-jmespath and mcp-tools-list-compression updated.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* refactor(mcp): keep describe_tool 60/min + unknown-tool hint in-band

Greptile P2: the trimmed describe_tool stanza dropped two pieces of
load-bearing guidance — the 60/min rate-limit caveat that qualifies
"use freely", and the {error: 'unknown_tool', available: [...]}
self-correction hint. The block comment above SERVER_INSTRUCTIONS
explicitly says stanzas must stand alone because LLMs don't reliably
fetch URLs mid-session, so both belong in-band.

SERVER_INSTRUCTIONS: 1397 B → 1577 B (+180 B). Net trim vs pre-PR
baseline: 1945 B → 1577 B (-368 B / -18.9%). Version-history comment
updated with the corrected delta and rationale.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>