docs(W4): apply fred's six contract decisions from PR #1350 comment 23693

A - docs/README.md:149-190 rewritten. It prescribed a competing front-matter schema
    (title/type/audience/status/source_of_truth) adopted by 4 of 128 live documents. Two
    documented conventions in one repo is the defect this pass removes, so the README now
    documents the contract and the 4 files convert in the same commit: `type` dropped
    (kind replaces it), `title`/`audience`/`source_of_truth` kept.
B - source-of-truth leaves the kind enum, which is now 6 values, and returns as an orthogonal
    boolean. kind was carrying two independent facts. docs/requirements/native-kanban-sot.md
    is stamped `kind: spec` + `source_of_truth: true`, which is what it always was.
C - status gains `completed`. Applied to the two executed plans, on artifact evidence rather
    than on their own say-so: --purpose push|merge ships in ci-queue-wait.sh, and every section
    the README plan specifies exists in docs/README.md today.
D - kind follows content, never filename. docs/native-kanban-sot/TASKS.md is `kind: spec`
    because its body says "a build plan, not a task tracker". The name stays wrong; that is a
    rename and it is out of scope here.
E - the contract covers .md only, written into the README as a decision with vision's
    YAML.parse measurement as the reason, so the omission does not read as an oversight.
F - channel-protocol.md guide -> spec. Applied, with a correction the reviewer should see: the
    ruling cites "7 normative MUSTs" and there are ZERO uppercase RFC2119 terms in that file.
    Control: the identical grep returns 25 lines in docs/requirements/native-kanban-sot.md. The
    citation half of the finding does hold and is larger than stated. Consequence recorded in
    the worklist: the file's own banner now contradicts its header.

Verified: 128 live .md under docs/ (127 baseline + this PR's worklist), 107 stamped, 0 invalid
kinds, 17 operator-held + 3 supersede-stamp deferrals + 1 generated = 21 unstamped. 107+21=128.
Control: the verifier reports valid=False when a kind is corrupted to `nonsense`, so the
0-invalid result is a real result. prettier --check clean across docs/.

docs/DEVELOPER-GUIDE/architecture/channel-protocol.md

@@ -1,5 +1,5 @@
 ---
-kind: guide
+kind: spec
 status: active
 ---
 

docs/DEVELOPER-GUIDE/testing/lease-broker-operations.md

@@ -2,7 +2,6 @@
 kind: guide
 status: active
 title: Lease-broker operations
-type: runbook
 audience: developer
 source_of_truth: false
 ---