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/test-verify-motion.py

@@ -402,7 +402,7 @@ def main() -> int:
             missing_guide = directory / "missing-guide.md"
             missing_guide.write_text(
                 original_skill.read_text(encoding="utf-8").replace(
-                    "### Visual-type guide (38)", "### Visual guide"
+                    "### Visual-type guide (39)", "### Visual guide"
                 ),
                 encoding="utf-8",
             )
@@ -410,7 +410,7 @@ def main() -> int:
             markdown_errors = semantic_module.verify_markdown()
         finally:
             semantic_module.SKILL = original_skill
-        if not any("must contain the 38-row visual-type guide" in error for error in markdown_errors):
+        if not any("must contain the 39-row visual-type guide" in error for error in markdown_errors):
             raise AssertionError(f"missing visual-guide anchor was accepted: {markdown_errors}")
         print("OK: missing visual-type guide anchor is rejected")