feat: add independently installable Rooms skill

[vks-archastro]

Review on ArchCode

Problem and author intent

Rooms should be adoptable without installing or learning the rest of ArchDev. A developer should be able to add one skill globally or to one repository, let it bootstrap the supported CLI, recover through login, and reach useful shared context immediately. Later teammates should run the same flow and join the same company Room.

This PR packages that onboarding and agent behavior in the public ArchDev distribution repository. It uses only the focused Rooms CLI supplied by the companion firstlanding PR; it does not add a daemon, resident agent, provider setup, repository configuration, or another runtime.

What changed

• Adds a public rooms skill with the recall-before-work and structured-exhaust participation contract.
• Documents global and repository-scoped installation with the standard npx skills add path.
• Adds Unix and PowerShell first-use bootstraps that reuse an existing compatible archdev, otherwise invoke the official installer and return the exact binary path.
• Pins the downloaded installer scripts to immutable repository commit 7c16002d66a004b13812cf675042cb1c50fbf6df; an explicit URL override remains only for controlled testing.
• Guides signed-out users through auth status and browser login, then connects without asking them to discover a Room ID.
• Makes the first-person and later-teammate behavior explicit, including server-authorized cross-organization membership.
• Directs the installed coding agent to read recent messages, search once, answer directly with message evidence, and publish only factual lifecycle updates.
• Clarifies that only a successful queue response guarantees durable storage; pre-queue connection failures require a later retry.
• Surfaces pending and rejected delivery state instead of treating a durable queue acknowledgement as delivery.

Scope

Public skill, bootstrap scripts, install documentation, and an acceptance test. No ArchDev runtime source, Platform API, server agent, web UI, or release workflow changes.

User impact

Users can install Rooms independently for their whole machine or one repository. On first use, the skill obtains a compatible ArchDev binary, recovers authentication, creates or joins the company Room, and opens recent team context. A coding agent can then answer questions from Room search results and publish structured start, done, lesson, abandoned, question, or handoff events.

The second and third same-organization users follow the identical command and automatically join shared history. Foreign Rooms require an explicit Room the Platform already exposes through membership or invitation.

Risk assessment

Low to medium. The package is additive and does not alter the existing installers. The bootstrap executes an immutable, reviewed installer script, and that installer verifies release checksums. The main risk is coordination with availability of the companion Rooms CLI release; bootstrap fails clearly if the installed/latest binary lacks the required lifecycle commands.

Testing

• tests/rooms-skill.sh — passed on macOS and now runs automatically in the existing Installer Smoke Test workflow on pull requests and main pushes.
• Skill validator — passed.
• PowerShell parser validation — passed.
• Verified both global and repository-scoped copies preserve the executable bootstrap.
• Verified the default bootstrap contains an immutable installer revision and rejects a mutable main-branch installer in the acceptance test.

Canonical end-to-end proof: tests/rooms-skill.sh. The script starts with isolated machine and repository directories, crosses the real npx skills add installation boundary in both supported scopes, starts without ArchDev or authentication, invokes a controlled official-installer stand-in, then follows the public skill through auth status, login, Room connect, recent recall, search evidence, and one queued lifecycle post. The companion core PR provides the built CLI/real TCP HTTP proof for those runtime commands.

Follow-ups and known issues

• Merge and release the companion core CLI before merging/publishing this skill; the bootstrap compatibility check intentionally rejects older binaries.
• Harness-owned PR evidence remains optional and is reused when a repository provides it. This skill does not reproduce that evidence system.
• Rejected post acknowledgement/cleanup can be added later; the current behavior favors persistent, honest warnings.