docs(adr): add ADR-0015 for outright APM conversion

Records the grill-with-docs decision on issue #88: replace the
hand-authored plugin/marketplace manifest model with Microsoft APM
(apm.yml + .apm/) as this repo's authoring source of truth. The
plugins/<name>/ monorepo-hybrid layout survives; marketplace.json and
provider plugin.json files become compiled output. Supersedes
ADR-0001; touches but does not resolve ADR-0006/0010/0014. Follow-up
work tracked in issues #89 and #90.

docs/adr/0015-apm-replaces-plugin-marketplace-authoring.md

@@ -0,0 +1,74 @@
+# Microsoft APM replaces the hand-authored plugin/marketplace model as this repo's authoring source of truth
+
+This repo replaces its hand-maintained Claude Code plugin/marketplace authoring model
+(`.claude-plugin/marketplace.json` + per-plugin `plugin.json`) with Microsoft APM (`apm.yml` +
+`.apm/`) as the authoring source of truth — an outright replacement of the authoring layer, not an
+additive overlay. This ADR records the decision from a `grill-with-docs` session on issue #88.
+
+## Context
+
+Every plugin under `plugins/<name>/` currently ships two hand-maintained manifests
+(`.claude-plugin/plugin.json` for Claude Code, root `plugin.json` for Copilot CLI) plus a
+hand-maintained root `.claude-plugin/marketplace.json` listing all plugins. Adding a provider means
+hand-authoring a third manifest shape; keeping the two existing ones in parity is itself a tracked
+concern (ADR-0006).
+
+Research on Microsoft APM (`plugins/kyberforge/docs/research/docs/microsoft-apm/`) found that its
+documented "monorepo-hybrid" repo shape maps directly onto this repo's existing `plugins/<name>/`
+layout: each plugin becomes its own `apm.yml` + `.apm/{skills,agents,hooks,prompts,instructions}/`
+package, listed from a root `apm.yml`'s `marketplace:` block. `apm compile`/`apm pack` generate
+per-target output — including a `.claude-plugin/marketplace.json` — from that vendor-neutral
+`.apm/` tree, so provider manifests become compiled artifacts instead of hand-authored files, and
+new providers (Copilot, Gemini, Codex — all supported by `apm runtime setup`) no longer require a
+new hand-maintained manifest format.
+
+## Decision
+
+- **The `plugins/<name>/` monorepo-hybrid directory layout survives.** `.claude-plugin/marketplace.json`
+  and per-provider `plugin.json` files become **compiled output** via `apm compile`/`apm pack`,
+  generated from `apm.yml` + `.apm/` per plugin, extensible to other `apm runtime`-supported
+  providers without hand-maintaining a separate manifest per provider.
+- **This directly supersedes ADR-0001** ("Skills are distributed via plugins... each plugin
+  contains its own `skills/` directory"). Once the real conversion executes, skills and agents
+  physically move to `plugins/<name>/.apm/skills/` and `plugins/<name>/.apm/agents/*.agent.md`.
+- New operational tooling — `apm-install` (skill), `apm-workflow` (skill), `apm-orchestrate`
+  (agent) — lands in `kyberforge`, tracked in issue #88
+  (https://git.dev.rkdr.net/Defame1297/holocron/issues/88).
+- Adapting `plugin-author`/`marketplace-author`/`skill-author`/`agent-author`/`forge`'s routing to
+  author `.apm/`-native content is deferred to issue #89
+  (https://git.dev.rkdr.net/Defame1297/holocron/issues/89).
+- Actually translating the existing plugins into `apm.yml` + `.apm/` and running the real
+  conversion is deferred to issue #90
+  (https://git.dev.rkdr.net/Defame1297/holocron/issues/90).
+- `CONTEXT.md`'s "Plugin"/"Skill"/"Plugin marketplace" glossary entries remain accurate as
+  written until issue #90 actually executes — this ADR does not update them.
+
+## Considered options
+
+**Additive/compile-layer only, no `apm.yml` (rejected).** Keep `plugin.json`/`marketplace.json`
+hand-authored and bolt APM on top as an optional extra. Rejected: doesn't achieve the multi-provider
+compile-reuse goal APM's package model provides, and leaves the existing dual-manifest hand
+maintenance in place unchanged.
+
+**New standalone `plugins/apm/` plugin (rejected).** `plugins/lint/` was split out of `kyberforge`
+specifically because Vale tooling is generic and repo-agnostic, not holocron-marketplace-specific
+(see `CONTEXT.md`'s "lint plugin" entry) — the same argument applies to a generic `apm` CLI
+wrapper. Rejected anyway, in favor of `kyberforge`, because this tooling's scope is specifically
+converting *this* repo's marketplace, not standing up a reusable generic apm toolkit for other
+repos. Accepted as an explicit tradeoff (same pattern as ADR-0011's `gitea-workflow` naming
+tradeoff) — worth revisiting if this tooling is ever reused outside holocron's own conversion.
+
+## Consequences
+
+- ADR-0001 is superseded once issue #90 executes.
+- ADR-0006 (plugin-version-parity) will need a third file, `apm.yml`, folded into its parity
+  check once #90 lands — not resolved by this ADR.
+- ADR-0010 (agent sources relocated outside agents dir) needs revisiting once agents move under
+  `.apm/agents/` with the `.agent.md` extension — not resolved by this ADR.
+- ADR-0014 (Vale prefilter ships from the plugin) has hardcoded path regexes assuming
+  `plugins/<name>/skills/...`/`plugins/<name>/agents/...`; these will need updating once paths
+  move under `.apm/` — not resolved by this ADR.
+- `kyberforge` gains three new artifacts (issue #88) before any conversion of existing content
+  happens.
+- Two follow-up issues (#89, #90) track the deferred authoring-tooling adaptation and the actual
+  repo conversion, respectively.