chore: drop redundant apm-marketplace-check and Copilot marketplace mirror (findings 1, 2)

apm-marketplace-check checked network reachability of remote marketplace
refs, but finding 35 already removed the only remote package entry, so
every marketplace.packages[] source is local and the hook is pure
overlap with apm-pack-check-clean. apm-audit-ci was re-examined and kept
as-is -- its pre-commit-config.yaml comment already carries a dated,
verified justification the audit had missed.

check-marketplace-mirror-sync guarded .github/plugin/marketplace.json
against drift from .claude-plugin/marketplace.json. Verified against
current GitHub Copilot CLI docs: Copilot's marketplace discovery already
falls back through .github/plugin/marketplace.json to
.claude-plugin/marketplace.json, which this repo generates anyway -- the
dedicated mirror bought a discovery-order preference, not a capability.
Deleted the mirror file, its sync script, its test, and the hook.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YR2CjVumUbEGWcMikcoXBD

.pre-commit-config.yaml

@@ -84,15 +84,6 @@ repos:
         pass_filenames: false
         always_run: true
 
-      - id: check-marketplace-mirror-sync
-        name: Check marketplace mirror sync
-        description: Verify .github/plugin/marketplace.json (Copilot CLI's legacy manifest path) is byte-identical to .claude-plugin/marketplace.json -- apm has no output profile for this path, so it must be kept in sync explicitly (see issue #90)
-        entry: bash scripts/sync-marketplace-mirror.sh --check
-        language: system
-        stages: [pre-push]
-        pass_filenames: false
-        always_run: true
-
       - id: check-executables-allow-sync
         name: Check executables allow key sync
         description: Verify root apm.yml's executables.allow key names kyberforge's actual version -- apm matches that key by exact "<package>#<version>" lookup, so a version bump on one side alone silently stops deploying kyberforge's hooks/ and bin/ and lets the apm install go stale (see ADR-0019)
@@ -102,15 +93,6 @@ repos:
         pass_filenames: false
         always_run: true
 
-      - id: apm-marketplace-check
-        name: apm marketplace check
-        description: Validate every marketplace.packages[] entry resolves, including network reachability of remote refs -- the only hook that checks remote package references rather than local-source paths
-        entry: apm marketplace check
-        language: system
-        stages: [pre-push]
-        pass_filenames: false
-        always_run: true
-
       - id: apm-audit-ci
         name: apm audit --ci
         description: Run apm's producer-side CI gate over the root manifest AND each of the six plugin packages. Verifies exactly two things per manifest -- apm.yml parses as a valid APM manifest (manifest-parse), and, if it declares dependencies, apm.lock.yaml exists and is consistent (lockfile-exists). It does NOT enforce an org policy and does NOT scan for hidden Unicode; see the comment below for why. Reference:plugins/kyberforge/.apm/skills/apm-workflow/references/audit.md
@@ -153,8 +135,8 @@ repos:
         # six plugin packages is what makes either reachable for them at all --
         # the root-only invocation audits the marketplace manifest and nothing
         # else. Costs ~0.5s per package, needs no network (checked under
-        # `unshare -rn`), so this does NOT join apm-marketplace-check and
-        # apm-pack-check-clean on the offline SKIP= list.
+        # `unshare -rn`) -- consistent with every other pre-push hook: none of
+        # them need the network (see README.md's "Offline?" section).
 
       - id: check-apm-agents-valid
         name: Validate real APM agent files