feat(fran-mora/plandex): add Plandex AI coding agent module

[fran-mora]

Summary

Adds the fran-mora namespace and a v1 plandex module that installs and configures the Plandex CLI in a Coder workspace. Plandex is an open-source CLI AI coding agent (Go, ~12k stars); this module fills a gap alongside the existing claude-code, aider, codex, opencode, goose, copilot, and cursor-cli modules.

Module shape mirrors claude-code:

• Wraps Plandex's official installer (https://plandex.ai/install.sh); supports pinned versions via the upstream PLANDEX_VERSION env var.
• Sets API-key env vars for OpenAI / Anthropic / Google / OpenRouter (each marked sensitive). Each coder_env resource is gated on the corresponding key being non-empty.
• Optional plandex_api_host for self-hosted Plandex servers.
• Optional workdir; auto-creates it if missing.
• Uses coder-utils for script orchestration per AGENTS.md guidance, with module data under \$HOME/.coder-modules/fran-mora/plandex/ per the standard data layout.
• Exposes the scripts output for downstream coder_script ordering via coder exp sync.

v1 ships CLI install only. Full agentapi web-UI integration is deferred until upstream coder/agentapi adds a plandex type; the README documents BYO-launcher via coder_app in the meantime.

The placeholder icon at .icons/plandex.svg and the namespace avatar are intentionally simple — happy to swap for an official asset if you have a preferred source.

Test plan

• terraform validate (from module dir) — pass
• terraform test -verbose — 11/11 pass (defaults, workdir trim, version pinning, install toggle, individual + multiple provider keys creating expected coder_env resources, self-hosted host, custom scripts, custom icon)
• bun run fmt — clean (no diff produced)
• go build ./cmd/readmevalidation && ./readmevalidation — pass (24 contributor profiles, 79 modules, 33 templates all valid)
• git diff --stat reviewed — only the 7 new files; no stray edits to existing code

Description of AI Usage

I used Claude Code to scaffold this module against the existing claude-code template, adapt it for Plandex's installer shape, write the test cases, and verify locally. All review comments are mine to address.