refactor(bin): cut per-invocation load and repair broken skill references

diagnose read its feedback-loops reference unconditionally, so every
invocation paid for guidance most runs never used; the read is conditional
again and the per-invocation cost drops from 1,278 to 831 words. Its HITL
template moves to assets/ because it is copied out, not read as reference.
prototype's two branch flows move into references/ for the same reason —
only one branch is ever taken.

research could not search the codebase it was asked to research without Grep
and Glob. caveman's description had grown into a paragraph where one sentence
carries the trigger. Four references pointed at things that do not exist: a
to-prd skill, a /setup-matt-pocock-skills command, two cross-skill ../ links
that only resolve in the source tree, and two places calling this project's
Gitea host GitHub.

Addresses #114.

plugins/bin/skills/triage/AGENT-BRIEF.md

@@ -1,6 +1,6 @@
 # Writing Agent Briefs
 
-An agent brief is a structured comment posted on a GitHub issue when it moves to `ready-for-agent`. It is the authoritative specification that an AFK agent will work from. The original issue body and discussion are context — the agent brief is the contract.
+An agent brief is a structured comment posted on an issue in the issue tracker when it moves to `ready-for-agent`. It is the authoritative specification that an AFK agent will work from. The original issue body and discussion are context — the agent brief is the contract.
 
 ## Principles
 
@@ -27,7 +27,7 @@ Describe **what** the system should do, not **how** to implement it. The agent w
 
 The agent needs to know when it's done. Every agent brief must have concrete, testable acceptance criteria. Each criterion should be independently verifiable.
 
-- **Good:** "Running `gh issue list --label needs-triage` returns issues that have been through initial classification"
+- **Good:** "Querying the issue tracker for the `needs-triage` label returns issues that have been through initial classification"
 - **Bad:** "Triage should work correctly"
 
 ### Explicit scope boundaries