feat(skills): size limits for agent writes + fuzzy matching for patch (#4414)

* feat(skills): add content size limits for agent-created skills

Agent writes via skill_manage (create/edit/patch/write_file) are now
constrained to prevent unbounded growth:

- SKILL.md and supporting files: 100,000 character limit
- Supporting files: additional 1 MiB byte limit
- Patches on oversized hand-placed skills that reduce the size are
  allowed (shrink path), but patches that grow beyond the limit are
  rejected

Hand-placed skills and hub-installed skills have NO hard limit —
they load and function normally regardless of size. Hub installs
get a warning in the log if SKILL.md exceeds 100k chars.

This mirrors the memory system's char_limit pattern. Without this,
the agent auto-grows skills indefinitely through iterative patches
(hermes-agent-dev reached 197k chars / 72k tokens — 40x larger than
the largest skill in the entire skills.sh ecosystem).

Constants: MAX_SKILL_CONTENT_CHARS (100k), MAX_SKILL_FILE_BYTES (1MiB)
Tests: 14 new tests covering all write paths and edge cases

* feat(skills): add fuzzy matching to skill patch

_patch_skill now uses the same 8-strategy fuzzy matching engine
(tools/fuzzy_match.py) as the file patch tool. Handles whitespace
normalization, indentation differences, escape sequences, and
block-anchor matching. Eliminates exact-match failures when agents
patch skills with minor formatting mismatches.

tests/tools/test_skill_manager_tool.py

@@ -271,7 +271,7 @@ class TestPatchSkill:
             _create_skill("my-skill", VALID_SKILL_CONTENT)
             result = _patch_skill("my-skill", "this text does not exist", "replacement")
         assert result["success"] is False
-        assert "not found" in result["error"]
+        assert "not found" in result["error"].lower() or "could not find" in result["error"].lower()
 
     def test_patch_ambiguous_match_rejected(self, tmp_path):
         content = """\
@@ -288,7 +288,7 @@ word word
             _create_skill("my-skill", content)
             result = _patch_skill("my-skill", "word", "replaced")
         assert result["success"] is False
-        assert "matched" in result["error"]
+        assert "match" in result["error"].lower()
 
     def test_patch_replace_all(self, tmp_path):
         content = """\