docs(skills): drop the Mode 2 routing notes, fix the contributing steps

Seven skills carried a `## Mode 2 Routing Note` citing a routing pod ("Plan 6")
that does not exist. Several admitted in their own text that nothing about the
skill changes between modes — so it was roughly ten lines of context on every
load for zero behavioural effect. The content is not worthless, just not
per-skill: it now lives as one table in README.md, with the caveat that nothing
depends on it.

The related line inside the session_log sections stays, because that one does
motivate behaviour — but it no longer cites a component that has never shipped.
It now says what is true: pass-rate is what a future routing decision would be
based on, and a skill that never logs contributes no evidence either way.

While in README: the contributing steps were stale enough to fail CI for anyone
who followed them. They said to add a row to SKILLS_INDEX.md by hand — the table
is generated now, and `task check` fails on a hand-edited diff — and listed none
of the four frontmatter keys the gates require. Step 4 now names the
pressure-test bar from #19 rather than leaving it to be discovered.

Closes #36
Bump-Type: patch

skills/cad-babysit/SKILL.md

@@ -247,12 +247,6 @@ decide
 - `fail` — the phase could not be completed (e.g. `cad stuck` errored, Gitea was unreachable).
 - `skip` — phase intentionally skipped (e.g. Phase 3 skipped because Phase 2 was conclusive).
 
-## Mode 2 Routing Note
-
-Phases 2-4 (reading comments/logs, classifying fault vs outcome) are judgment-heavy and should
-stay Mode 1. Phase 1 (running `cad stuck` and grouping its output) is mechanical and a Mode 2
-routing candidate once Plan 6 ships the routing pod.
-
 ## Cross-References
 
 - Depends on `mathias/cad#14`'s `cad stuck` query — this skill is the ritual around it, not a