refactor(bin): retrofit research to the ADR-0020 context contract

Description 583 -> 231 chars and body 854 -> 519 words. Deletes the
neuledge-context boundary clause outright: commit 6146120 deleted that
skill and no skill has owned MCP-server installation since. That was the
last dangling routing target in the corpus.

Removes META.md, which file-structure.md:20 forbids at a skill root. Its
when: field duplicated the description and its references: entry pointed
at .agents/skills/context7-mcp/SKILL.md, which does not exist.

Restores two rules a clean-context audit found had lost their force: the
starting-URLs branch in step 3, which the retrofit had reduced to a
condition with no behaviour, and the references/file-format.md pointer at
step 6. The second matters downstream -- validate-provenance.sh parses
sources.md with anchored regexes and check 8 short-circuits silently when
the Status field is absent, so a sources.md written from step 6 alone
broke the provenance chain with no error anywhere.

Rewrites steps 4-5 as serial WebFetch reads. They mandated spawning
subagents that allowed-tools never granted; no tool was added because the
name differs across the three compile targets. Tracked as #116.

Updates the two test pins and the eval case that asserted the dead route.

Refs #99

plugins/bin/evals/research/research/eval.yaml

@@ -26,11 +26,6 @@ trigger_tests:
     query: "Research why these integration tests are failing"
     should_trigger: false
 
-  - id: negative-neuledge
-    name: "Negative — MCP server setup goes to neuledge-context"
-    query: "Install the neuledge context server and set it up"
-    should_trigger: false
-
   - id: negative-context7-direct-question
     name: "Negative — direct doc question goes to context7-mcp, not research"
     query: "What are the Next.js middleware options?"