docs(kyberforge): narrow issue #89 scope, migrate CC platform facts to apm-workflow

A grill-me session determined plugin-author/marketplace-author are fully
superseded by the landed apm-install/apm-workflow/apm-orchestrate artifacts
and will be deleted (not adapted) under issue #90, narrowing issue #89 to
skill-author/agent-author only; forge stays untouched. ADR-0015 is amended
to record this correction plus a three-way content-migration audit.

Claude Code platform-constraint facts that lived only in
plugin-author/marketplace-author (reserved name prefixes, the ADR-0010
agents/ stray-.md validator gotcha, claude plugin validate as a terminal
check, and a removal/re-pack confirm-before-proceeding note) remain true
post-conversion and are migrated into apm-workflow's reference docs via
kyberforge:skill-author, which also updated the skill's README and
sources.md provenance records. Dual-manifest-specific conventions (ADR-0006
parity, CC/Copilot field-placement split) do not carry forward since they
no longer apply.

ADR: 0015

plugins/kyberforge/skills/apm-workflow/references/sources.md

@@ -7,3 +7,27 @@
 - **Research doc:** plugins/kyberforge/docs/research/docs/microsoft-apm/sources.md
 - **Contributing files:** SKILL.md, references/configure.md, references/install.md, references/marketplace.md, references/compile.md, references/audit.md
 - **Status:** `extracted`
+
+## context7-websites-code-claude
+
+- **URL:** context7:/websites/code_claude
+- **Description:** Official Claude Code documentation site indexed by Context7 — marketplace manifest schema (reserved name prefixes), `claude plugin validate` command behavior. Claude Code platform facts that hold true independent of how the compiled manifest is authored (APM or hand-authored).
+- **Research doc:** plugins/kyberforge/docs/research/docs/claude-code-plugins/sources.md
+- **Contributing files:** references/marketplace.md, references/audit.md
+- **Status:** `extracted`
+
+## claude-code-plugins-docs
+
+- **URL:** https://code.claude.com/docs/en/plugins
+- **Description:** Official Claude Code plugin authoring guide — marketplace submission constraints (reserved name prefixes), `claude plugin validate` behavior and its scope relative to other CI checks.
+- **Research doc:** plugins/kyberforge/docs/research/docs/claude-code-plugins/sources.md
+- **Contributing files:** references/marketplace.md, references/audit.md
+- **Status:** `extracted`
+
+## claude-code-subagents-docs
+
+- **URL:** https://code.claude.com/docs/en/sub-agents
+- **Description:** Official Claude Code subagent reference — definition format, all frontmatter fields, scope priority, built-in agents, CLI flags, environment variables, known limitations
+- **Research doc:** plugins/kyberforge/docs/research/docs/claude-code-plugins/sources.md
+- **Contributing files:** (none)
+- **Status:** `referenced`