Drop strategy/ as a division — it's playbooks/runbooks, not agents (#595)

strategy/ holds 16 markdown files and ZERO have agent frontmatter — they're
playbooks (playbooks/phase-*.md), runbooks (runbooks/scenario-*.md), and briefs
(EXECUTIVE-BRIEF.md, QUICKSTART.md, nexus-strategy.md), not agent definitions.
There are 16 real agent divisions, 232 agents; strategy is not one of them.

#592 added `strategy` to lint-agents.sh AGENT_DIRS and the lint workflow paths
(to match divisions.json), which made CI lint those 16 frontmatter-less docs as
agents and fail every one with "missing frontmatter opening ---". So any PR
touching strategy/ broke CI. The original lint-agents.sh correctly excluded
strategy; #592 misread that deliberate exclusion as drift (same mistake as
integrations/ in #593).

Fix: remove strategy from convert.sh / lint-agents.sh AGENT_DIRS, the lint
workflow, and divisions.json; add it to NON_DIVISION_DIRS in check-divisions.sh.
divisions.json is now 16, matching the app's parse_agent count exactly.

Also add a content-derived backstop to check-divisions.sh: every division must
contain at least one .md with '---' frontmatter, or the build fails. This is
what stops a docs/playbook directory from being registered as an empty agent
division again — regardless of whether someone remembers the exclude list.

check-divisions.sh PASSES at 16; negative-tested that re-adding strategy fails
with "division 'strategy' has no agent files".

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

divisions.json

@@ -1,5 +1,5 @@
 {
-  "_note": "Source of truth for the agent division set. Each division (a top-level agent directory) maps to a display label, a Lucide icon name (PascalCase), and a brand color (hex). Consumed by the Agency Agents app and any other catalog tooling. scripts/check-divisions.sh (CI: check-divisions.yml) fails the build if this list disagrees with the directories on disk, the AGENT_DIRS arrays in scripts/convert.sh and scripts/lint-agents.sh, or the path filters in lint-agents.yml. To add a division: create its directory, add an entry here, then run scripts/check-divisions.sh and update wherever it points. NOT every top-level directory is a division: integrations/ holds per-tool conversion OUTPUTS written by scripts/convert.sh (not source agents) and is excluded via NON_DIVISION_DIRS in check-divisions.sh; examples/ and scripts/ are likewise excluded.",
+  "_note": "Source of truth for the agent division set. Each division (a top-level agent directory) maps to a display label, a Lucide icon name (PascalCase), and a brand color (hex). Consumed by the Agency Agents app and any other catalog tooling. scripts/check-divisions.sh (CI: check-divisions.yml) fails the build if this list disagrees with the directories on disk, the AGENT_DIRS arrays in scripts/convert.sh and scripts/lint-agents.sh, or the path filters in lint-agents.yml. To add a division: create its directory, add an entry here, then run scripts/check-divisions.sh and update wherever it points. NOT every top-level directory is a division: integrations/ holds per-tool conversion OUTPUTS written by scripts/convert.sh (not source agents); strategy/ holds playbooks and runbooks with no agent frontmatter; both — plus examples/ and scripts/ — are excluded via NON_DIVISION_DIRS in check-divisions.sh. A division must contain at least one frontmatter agent file.",
   "divisions": {
     "academic": { "label": "Academic", "icon": "GraduationCap", "color": "#8B5CF6" },
     "design": { "label": "Design", "icon": "PenTool", "color": "#EC4899" },
@@ -15,7 +15,6 @@
     "security": { "label": "Security", "icon": "ShieldCheck", "color": "#EF4444" },
     "spatial-computing": { "label": "Spatial Computing", "icon": "Boxes", "color": "#06B6D4" },
     "specialized": { "label": "Specialized", "icon": "Sparkles", "color": "#6366F1" },
-    "strategy": { "label": "Strategy", "icon": "Network", "color": "#F43F5E" },
     "support": { "label": "Support", "icon": "LifeBuoy", "color": "#84CC16" },
     "testing": { "label": "Testing", "icon": "FlaskConical", "color": "#F59E0B" }
   }