SPEC.md's get_explainer table row says it reads explainers/<slug>.md, contradicting the code

[yakew7]

Where: faircode/SPEC.md:392 (the get_explainer MCP tool table row) vs. faircode/mcp_server.py:60 (EXPLAINERS_DIR) and its actual read path for a given slug.

The gap: the table says get_explainer wraps explainers/<slug>.md (a repo-root path). The code actually reads from faircode/_explainers/<slug>.md - the same package-internal mirror the companion list_explainers issue describes, built by scripts/build_explainers.py specifically because explainers/ isn't shipped by pyproject.toml (issue #388).

Repro:

$ grep -n "EXPLAINERS_DIR" faircode/mcp_server.py
60:EXPLAINERS_DIR = Path(__file__).resolve().parent / "_explainers"
$ grep -n "get_explainer" faircode/SPEC.md
392:| `get_explainer` | `explainers/<slug>.md` | ...

EXPLAINERS_DIR resolves to faircode/_explainers/, not the repo-root explainers/ the table names.

Why it matters: same category as the list_explainers row and the already-fixed get_benchmark_results row (#434) - a reader trusting this table gets the wrong idea of what a real installed package reads from, contradicting SPEC.md's own surrounding explanation of why the package-internal mirrors exist.

Suggested fix: update the table cell to faircode/_explainers/<slug>.md (mirrored from explainers/<slug>.md).