test(mcp): prove tracedecay_search behavior

[ScriptedAlchemy]

Summary

• Proves tracedecay_search through the production MCP tools/call path, not a handler stub.
• A query for apply_invoice_discount must return that function ahead of apply_invoice_discount_preview, with kind function and path src/billing.rs.
• An unknown name returns no symbols while coverage stays complete, and a call without query is an invalid-params refusal.

Motivation

The tool is the host entry point for symbol search. Existing suite coverage polls it for readiness and checks schema, but does not pin the ranked symbol a host actually observes.

Changes

• crates/tracedecay/tests/mcp_suite/mcp_handler_test/search_behavior_test.rs calls the production server with one fixture and literal expectations for the hit, the decoy order, the miss, the default markdown rendering, and the missing-query error.

Test plan

• scripts/require-exact-test.sh cargo test -p tracedecay --features test-transport --test mcp_suite mcp_handler_test::search_behavior_test::exact_name_search_returns_that_function_and_rejects_a_missing_query -- --exact
• Full workspace suite not run; this change is one MCP behavior test.

Checklist

• CHANGELOG.md updated (under [Unreleased] if no version bump) — not applicable, test only
• No secrets, credentials, or .env files included
• Breaking changes documented (if any) — none

  

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[ScriptedAlchemy]

Closing as superseded. A sibling change proving the same tool landed first as #1664.

Evidence from the triage: git log origin/master --diff-filter=A -- mcp_handler_test/search_behavior_test.rs => de3b561, carried by 829850a 'merge: PR #1664 test(mcp): prove tracedecay_search behavior'; same path added in both, 3 conflict hunks

Reopen if the landed version misses an assertion this branch carries; name it and it can be ported as a small follow-up.