docs: stop typing versions the code already knows

Nine documents carried a hand-typed contract version and every one was stale.
One was load-bearing: PLUGIN-EXTERNAL-REPO.md told an external author to pin
">=0.13.0,<0.14.0" while the contract is at 0.19.0, so a plugin built by
following that guide is refused by the loader at startup. The plugin count was
wrong in six more.

They now point at docs/PROJECT-MAP.md, which is generated. A test enforces it:
no document may declare a version literal, a stated current version must match
the code, and a stated plugin count must match the tree. ADRs are exempt from
the current-version rule, because an ADR states the version a decision was taken
AT - that is a record of the past, and rewriting it would falsify the record
ADRs exist to keep.

CONTRACT-STABILITY.md was missing 0.17.0, 0.18.0 and 0.19.0 - including the only
BREAKING change in the series - in the one document a site reads to choose its
pin. All three are recorded, with 0.19.0 called out: it took something away, and
it shipped before it was written down, which is the argument for pinning tight
rather than trusting that a minor bump is safe.

docs/DEPLOY-WINDOWS-IIS.md

@@ -115,7 +115,7 @@ venv\Scripts\flask seed reference-data
 
 # Install the plugins this site tracks (registry lives in the gitignored
 # instance/plugins.json, so a fresh box starts with none installed). Run
-# `flask plugin list` to see the current bundled set; the 13 bundled plugins are
+# `flask plugin list` to see the current bundled set; the the bundled plugins are
 # computers, employees, geenforce, knowledgebase, machines, measuringtools,
 # network, notifications, printedparts, printers, slides, usb, warranty. Install
 # only the ones this site wants: