Refresh docs: readme, PITCHME, docs/ pages, about_PSGraph help topic

[exactmike]

Summary

• readme.md: full 16-command list (was only 5 of 16), grouped and linked; pointer to Get-Help about_PSGraph
• docs/Command-Cells.md: new page for the one exported command with no doc page; wired into mkdocs.yml's nav
• Fixed unrelated bugs found while spot-checking: docs/index.md said "PSDeploy", docs/graphviz.md was completely empty despite being linked in the nav, and Command-Record/Row/Entity.md referenced images at a /img/ path that never existed anywhere in the repo (regenerated the four images for real via Export-PSGraph)
• PITCHME.md: rewritten for the fork (was 100% upstream-original, pointing at kevinmarquette/psgraph — GitPitch itself has been discontinued since 2020), expanded into a gallery of 6 runnable examples (server farm, DB schema, live process tree, service deps, module deps, multi-format export), each verified by actually running it against the module; deleted PITCHME.yaml
• PSGraph/en-US/about_PSGraph.help.txt: new conceptual help topic, verified via Get-Help about_PSGraph
• Follow-up fix: PITCHME.md's image paths were copied from the docs/-relative convention without adjusting for PITCHME.md's location at the repo root, breaking rendering in VS Code/GitHub preview — fixed

Test plan

• Get-Help about_PSGraph renders correctly after Import-Module in dev mode
• Every example in PITCHME.md and the about_PSGraph EXAMPLES block run successfully against the module with GraphViz installed
• Every image reference in PITCHME.md and the three fixed Command-*.md pages resolves to a real file
• Every markdown page referenced in mkdocs.yml's nav exists on disk
• Reviewer: preview PITCHME.md and readme.md rendering on GitHub

https://claude.ai/code/session_01JkdNkQkbr85iif33Q964JX