Finish ystack public rebrand with pstack compatibility - #5

What changed

• promote ystack as the public repository, install target, and primary skill entry;
• add /ystack and /setup-ystack skills;
• retain /pstack and /setup-pstack as explicit compatibility aliases;
• prefer ystack-models.* override files while continuing to read legacy pstack-models.* and codex-pstack-models.md paths;
• update README, install instructions, contributor guidance, coverage, guides, license, notice, and the model schema ID;
• add a CI branding guard that rejects the retired Go7hic/pstack repository slug and verifies the public/legacy entry files;
• mark public and compatibility skills as hand-maintained during upstream imports.

Naming boundary

• Public name: ystack
• Upstream lineage: Cursor pstack
• Legacy compatibility: pstack, setup-pstack, and pstack-models.*
• Shared internal runtime path for now: skills/pstack/

Keeping the internal runtime path avoids a large breaking migration while making every new user-facing surface consistently ystack.

User impact

New installs use:

npx skills add Go7hic/ystack -g -s '*' -y

Primary commands are:

/ystack
/setup-ystack

Existing prompts and model configuration remain usable through compatibility aliases and adapter fallbacks.

Validation

The repository workflow checks:

• ystack branding and compatibility invariants;
• mirror consistency;
• strict portable-skill audit;
• Markdown relative links;
• model override fixtures;
• import idempotency;
• upstream manifest shape.

Review focus

• whether the compatibility window is explicit enough;
• whether keeping skills/pstack/ as the shared internal runtime path is the right low-risk migration boundary;
• whether any public documentation still presents pstack as the repository name rather than upstream lineage or compatibility.