chore: track the hallmark skill's pointer and lockfile

`.agents/skills/hallmark/**` has been committed since the landing-page
work, but the two files that make it resolve were left untracked: the
`.claude/skills/hallmark` symlink Claude Code reads, and
`skills-lock.json`, which records where the skill came from and the hash
it was installed at.

So a fresh clone carried the skill's content and no way to load it — the
design gates that shaped the landing page were present but invisible to
the agent meant to apply them, and nothing recorded that hallmark is
`nutlope/hallmark` at a pinned hash rather than local prose.

The symlink is relative (`../../.agents/skills/hallmark`), so it resolves
in any clone. This matches the virgil checkout, which tracks the same
three things — the skill body, the `.claude/skills` pointer, and
`skills-lock.json`.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: angusbezzina

.claude/skills/hallmark

@@ -0,0 +1 @@
+../../.agents/skills/hallmark

skills-lock.json

@@ -0,0 +1,11 @@
+{
+  "version": 1,
+  "skills": {
+    "hallmark": {
+      "source": "nutlope/hallmark",
+      "sourceType": "github",
+      "skillPath": "skills/hallmark/SKILL.md",
+      "computedHash": "579f86b27cdd7eb972107f7aecedd537f472891c5fd7c7c821bea15f64e0fe86"
+    }
+  }
+}