feat: consolidate reviewed Diagram Design 2.6.0 release (#134)

* fix(commands): stop hardcoding the visual-type count

Integrates the final reviewed diff from PR #112.

* docs(high-level): correct effective width checklist

Integrates the final reviewed diff from PR #105.

* fix(commands): quote profile argument hint

Integrates the final reviewed diff from PR #126.

* test(sankey): gate conservation and ribbon geometry

Integrates the final reviewed diff from PR #103.

* feat(tooling): add doctor diagnostics gate

Integrates the final reviewed diff from PR #132.

* feat(scripts): lint diagrams as rendered

Integrates the final reviewed diff from PR #18.

* feat(types): add quantitative polar chart

Integrates the final reviewed diff from PR #101.

* chore(release): consolidate reviewed changes in 2.6.0

Documents every combined gate and synchronizes Claude, Codex, and Factory metadata for the 39-type release.

* fix(doctor): support installed-skill projects

---------

Co-authored-by: mysoniw <soniw1@gmail.com>
Co-authored-by: thang <76550342+thangldw@users.noreply.github.com>
Co-authored-by: YinShaokun <yinshaokun@didiglobal.com>
Co-authored-by: 0xDarkMatter <0xDarkMatter@users.noreply.github.com>
Co-authored-by: Rupam Pal <rupam.pal@euromonitor.com>
Co-authored-by: Yuvraj3905 <yuvraj202001@gmail.com>

scripts/verify-screenshot-freshness.py

@@ -20,8 +20,8 @@ from screenshot_catalog import (
 def main() -> int:
     errors: list[str] = []
     slugs = canonical_slugs()
-    if len(slugs) != 38 or len(slugs) != len(set(slugs)):
-        errors.append(f"expected 38 unique canonical types; found {len(slugs)}")
+    if len(slugs) != 39 or len(slugs) != len(set(slugs)):
+        errors.append(f"expected 39 unique canonical types; found {len(slugs)}")
 
     if not MANIFEST.is_file():
         errors.append("docs/screenshots/manifest.json is missing")
@@ -96,7 +96,7 @@ def main() -> int:
         for error in errors:
             print(f"  - {error}")
         return 1
-    print("OK screenshot freshness: 38 canonical sources and PNG digests match")
+    print("OK screenshot freshness: 39 canonical sources and PNG digests match")
     return 0