fix(ci): untrack .venv symlink and align Beam avatar contract

The staging gate failed on READ_ERROR .venv after a docs commit tracked a
symlink that gitignore .venv/ does not ignore. CI replaces that path with a
real venv directory. Drop the symlink, ignore the name itself, and lock it
in the privacy scan. Also point the Beam avatar source contract at the
current profile-panel copy so npm test stops failing after Python.

frontend/tests/beam-avatar.test.ts

@@ -94,7 +94,7 @@ test("renders the persisted Beam avatar in the sidebar, account menu, and profil
   assert.match(sidebar, /<UserAvatar avatar=\{account\.avatar\} size=\{32\}/);
   assert.match(sidebar, /<UserAvatar avatar=\{account\.avatar\} size=\{40\}/);
   assert.match(page, /<ProfilePanel[\s\S]*persistAvatar=\{persistAvatar\}/);
-  assert.match(profilePanel, /Beam 形象由随机种子生成/);
+  assert.match(profilePanel, /Beam 形象会在刷新和换设备后保持一致/);
   assert.match(profilePanel, /role="radiogroup" aria-label="头像配色"/);
   assert.match(profilePanel, /persistAvatar\(\{ action: "set_palette", palette: index \}\)/);
   assert.match(profilePanel, /persistAvatar\(\{ action: "randomize" \}\)/);