Make just the single front door; add ADR/RFC/PRD decision records

Andrew Dunnrequested to merge
decision-records into main

What

Two related changes, ahead of the v1.0.0 tag:

  1. just becomes the single front door. SKILL.md scopes execution to allowed-tools: Bash(just *), but gce.md drove the tool via simulator.sh and an ad-hoc-shell note recommended calling the engine directly to work around a real bug (just ssh -- "<cmd>" flattens variadic args and drops quoting). That contradiction would have frozen into the interface at 1.0.0.
  2. Decision-record formats so contributors know how to propose and record changes.

One front door

  • New ssh-cmd recipe passes a single command through {{quote()}}, preserving quotes and pipes (dogfooded live on a VM: a curl -H 'PRIVATE-TOKEN: …' reaches the VM intact). ssh *args stays for flags, interactive use, and port-forwards.
  • gce.md command catalog and ad-hoc-shell guidance rewritten to just form; complex ssh -- examples in SKILL.md, gce.md, seeding.md, README.md converted to ssh-cmd; simulator.sh named as the engine just wraps, not a way to drive the tool.
  • allowed-tools unchanged (Bash(just *)) — docs, tool-scope, and examples now agree.

Decision records

  • docs/{adr,rfc,prd}/ each with a README + TEMPLATE; a docs/README.md index (when to use which, how to add); a CONTRIBUTING.md pointer.
  • Seed ADR-0001 records the single-front-door decision (dogfoods the ADR format).

Checks

just ci clean; Vale runs in the MR pipeline. ssh-cmd's {{quote()}} behavior validated locally and live.

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