Stop emitting redundant filename/slug fields in MCP read-tool responses

[ivklgn]

Problem

The document model serializes filename and slug on every row the read tools return, without omitempty. Both are derivable from path, which is already present. The list_documents description does not mention them, so only the wire payload carries the redundancy.

The struct moved in v0.7.0: it is docs.Document in internal/docs/document.go (aliased as LocalDocument in internal/mcp/tools/docs_bridge.go), not internal/mcp/tools/common.go.

Internal consumers — already checked

Both fields are read inside the binary, so they cannot be deleted outright:

• Slug — internal/advisory/code_alignment.go, which turns a slug into search tokens
• Filename — cmd/status.go, in the naming check

The change is therefore json:"-" on both fields, keeping the Go fields in place.

Expected result

Read-tool JSON payloads omit filename and slug. The Go struct keeps them for internal use.

Impact

~430 tokens per 50 documents on list_documents and search_documents — among the most frequently called tools. Item 2 in .archcore/cli/mcp-token-optimization.idea.md.

Scope

• Mark both fields json:"-" in internal/docs/document.go.
• Check search_documents and get_document for their own copies of the fields in response structs.
• Update the output-shape tests, and the examples/ fixtures if they pin the payload.

Files: internal/docs/document.go (+ list/search/get tests)

Acceptance: read-tool payloads omit filename and slug, and the integration suite passes.