Document the seven dimensions in the directory README (V-725)

The rebuild section named the new inputs and nothing said what the columns
mean or how a partial arises.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/capabilities/README.md

@@ -36,6 +36,30 @@ name, a `domains.yaml` row naming a capability that does not exist, a
 outside the five, and a reason outside the plan's list. It caught the domain
 reconciler silently dropping `recall` from its 51.
 
+It also fails on a capability missing from `implementation.yaml`, a component id
+that `docs/architecture/maven-architecture.json` does not carry, and a component
+status the dimension table does not know. A capability absent from the mapping
+would read `no` on every dimension, which is indistinguishable from a capability
+nothing carries.
+
+## The seven dimensions
+
+Never one `implemented` boolean. Coded and unwired, wired and unconfigured, and
+configured and undeployed are three different pieces of work.
+
+`designed`, `code_present`, `wired`, `configured`, `deployed` and `reachable`
+come from the `status` field of every component mapped to the capability, rolled
+up as all yes, none no, otherwise partial. `verified` comes from the criteria
+verdicts: yes when every one passes, partial when some do.
+
+`designed` answers a narrower question, because `docs/spec.md` states all 51 of
+them. It reads `yes` when a living doc owns the subsystem, and `spec-only` when
+the State line says no living doc or no package.
+
+A component the mapping does not use is reported by name at the end of a build.
+Shared infrastructure is excluded on purpose: mapping `core.reactive_handler` to
+everything would give all 51 rows the same status and say nothing.
+
 ## Running the probes
 
 The probes run **on homesrv**, where mavweb is on `127.0.0.1:9201` and the