fix(kyberforge): fix scope walk-up and manifest-parsing bugs from PR #93 review

A fresh /code-review of the APM-native authoring retarget (PR #93) found
several correctness bugs beyond the ones already fixed on this branch:

- new-agent.sh silently walked a marker-less subdirectory under $HOME up
  to user scope, contradicting its own usage text ("user scope is checked
  directly, no walk-up") and risking scaffolding into shared global
  ~/.claude or ~/.copilot directories instead of the intended local path.
- The hand-copied apm.yml type: manifest detector in new-agent.sh and
  new-skill.sh accepted mismatched quotes (e.g. `type: "skill'`) that
  validate.sh's regex correctly rejects, and silently dropped a final
  apm.yml line lacking a trailing newline — causing the scaffolder and
  validator to disagree on scope for identical input.
- Plugin-scope agent frontmatter could still contain the apm-agent.md
  template's HTML comments at ship time with no audit signal, yet
  apm compile copies frontmatter verbatim and <!-- --> breaks YAML
  parsing on both downstream harnesses.
- ADR-0016 asserted agent-audit already implements a SUGGESTION heuristic
  for tool-restriction-needing plugin-scope agents; it doesn't.
- agent-audit/README.md still described the old plugin-pair model this
  PR replaced with a single-file allowlist model.
- validate.sh's project/user-scope CC-only/Copilot-only field checks and
  counterpart-missing check lost their only test coverage when the old
  plugin-pair fixture was deleted.

Also replaces an echo-into-sed two-value parse (4 forks per call) with a
single space-separated echo + read in both scaffolders.

Regression tests added for every fix above, including one for a bug this
pass introduced and the test suite caught: an initial two-line
echo + `read` attempt silently dropped the second value, since `read`
consumes only one line regardless of embedded newlines.

Full suite: 158 bats tests, 39 shell-script tests, 12/12 summary
categories, 0 failures.

Refs: #89, #93

plugins/kyberforge/skills/agent-audit/scripts/validate.sh

@@ -185,6 +185,17 @@ def check_apm_agent_file(fpath, allowlist, stem):
         fail(f"no valid YAML frontmatter (---...---) — {local_fname}")
         return
 
+    # The apm-agent.md template embeds its authoring guidance as HTML
+    # comments inside the frontmatter block (so they render invisible in a
+    # Markdown preview but stay visible in the raw file). get_frontmatter_keys
+    # silently ignores any line that isn't a `key:` match, so a comment left
+    # behind at ship time would otherwise pass unnoticed — yet apm compile
+    # copies this frontmatter verbatim to both harnesses, and `<!-- -->` is
+    # not valid YAML, so yaml.safe_load breaks on both downstream (ADR-0016).
+    if re.search(r'<!--|-->', fm):
+        fail(f"frontmatter still contains template HTML comments (<!-- ... -->) "
+             f"— delete them before shipping — {local_fname}")
+
     # Allowlist: only name/description/model may appear — no tools, no
     # Claude-only or Copilot-only fields. apm compile verbatim-copies
     # frontmatter to every target, so anything else is unsafe on at least