feat(gtm): add mandatory knowledge-base read/write directives to GTM skills

Agents must now read client profiles before GTM work and write session
logs after completing audits, tag changes, or validation — ensuring
findings compound across sessions instead of being lost.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.claude/commands/gtm-editor.md

@@ -22,6 +22,20 @@ Priority reads per task:
 - "create GTM tag", "generate dataLayer", "modify trigger"
 - "update variable", "write custom HTML", "manage GTM"
 
+## MANDATORY: Knowledge Base Read/Write
+
+**Before creating or modifying ANY tags, triggers, or variables:**
+1. Identify the target client from container ID
+2. Read `knowledge-base/accounts/<client>/profile.md` — key variables, URL patterns, platform stack, known issues
+3. Read `knowledge-base/accounts/<client>/*.md` — taxonomy reveals existing event names and naming conventions
+4. Skim `knowledge-base/logs/<client>/` — past fixes reveal patterns (e.g., "form POST loses URL params")
+
+**After completing tag management, write a session log:**
+- Write to `knowledge-base/logs/<client>/YYYY-MM-DD-<description>.md`
+- Include: date, container ID, tags affected (IDs), what was created/modified/deleted, cHTML snippets
+- Update `knowledge-base/accounts/<client>/profile.md` if you discovered persistent facts
+- See `AGENTS.md` for full format template
+
 ## MANDATORY: dataLayer First Workflow
 
 1. **Design dataLayer push FIRST** (match client's tech stack: vanilla JS/React/Vue/PHP)