docs(chat): integrate Discord adapter into registry and project template

[onlyarnav]

Part 2 of 2 in the contract:chat Discord adapter stack (preceded by #1484).

Summary

• Integrates tools/chat-discord into the chat contract documentation (tools/chat/README.md), marking discord as a shipping adapter alongside slack.
• Documents Discord bot token under $HOME (~/.config/apache-magpie/discord-token or $DISCORD_BOT_TOKEN) in tools/chat/README.md prerequisites credentials.
• Adds chat.guild_id (commented out by default) and clarifies channel names (with Discord IDs accepted) in plugins/magpie-setup/templates/project.md and tools/chat/README.md.
• Updates docs/adapters/registry.md chat row to list tools/chat-discord/ as shipping, with Matrix (feat(tools/matrix): chat bridge for projects whose primary chat is Matrix / Element #309) and Zulip (feat(tools/zulip): chat bridge for projects whose primary chat is Zulip #308) tracking links.
• Updates spec-loop specifications (tools/spec-loop/specs/adapters.md and contributor-growth.md) to reflect Discord as a shipping adapter alongside Slack, noting Matrix and Zulip remain extension points.

Type of change

• Documentation / process (docs/, README.md, comments)
• Tool / bridge contract (tools/<system>/*.md)

Test plan

• Verified links and references across updated documentation and templates.
• Ran doctoc TOC generation and markdownlint-cli2 across all modified Markdown files.
• Verified SPDX license headers.
• Ran spec-validate on tools/spec-loop/specs/.

RFC-AI-0004 compliance

• Write-access discipline — purely documentation and templates; no code changes.
• Vendor neutrality — reflects the dual-backend status of contract:chat.
• External content as data — maintains untrusted data discipline for chat messages across specs and contracts.

Linked issues

Closes #1421

🤖 Generated with Antigravity

[potiuk]

Thanks for wiring the Discord adapter from #1484 into the docs — the links to tools/chat-discord/ resolve once #1484 lands, and the stack is in order. Two things need fixing before this merges: a wrong tracking link in the adapter registry (inline), and spec text that now contradicts itself.

The contributor-growth spec now contradicts itself

The specs in tools/spec-loop/specs/ are the source of truth and must not fall behind the code.
— AGENTS.md

In tools/spec-loop/specs/contributor-growth.md the frontmatter source: and the Known-gaps bullet now say chat covers Slack and Discord, but two passages the diff doesn't touch still say otherwise:

• Where it lives → Tools bullet: `tools/chat-slack` (Slack MCP adapter, public channels only, never posts). Discord is an extension point with no adapter yet.
• Behaviour & contract → Community signals: chat answers through `contract:chat` (Slack adapter; public channels only).

Please add tools/chat-discord (Discord MCP adapter, public channels only, never posts) to the Tools bullet, drop the "Discord is an extension point" sentence, and change "(Slack adapter; …)" to "(Slack or Discord adapter; …)".

Smaller observations

• See inline on specs/adapters.md and the project template (chat.guild_id).
• tools/chat/README.md → Prerequisites → Credentials / auth still describes only the Slack connector; please add a clause for the Discord adapter.
• The PR description lists docs/labels-and-capabilities.md changes, but those are in #1484 — please correct it so the stack's descriptions match their contents. And consider "Closes #1421" on whichever stack PR lands last, so the adapter issue closes when the work ships.
• Any change to #1484's coverage (see the review there) flows into the "shipping" wording here.

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[potiuk]

Thanks — all three earlier threads, the contributor-growth spec contradictions, and the Credentials clause are fixed. Two small config-wording issues remain inline (guild_id shipping as an active "..." value, and "channel names or IDs" promised contract-wide while the Slack adapter resolves names only), plus a nit. Merge still waits on #1484.

The PR description still says this PR marks contract:chat vendor-neutral and moves the score to 11/12 — that change now lives in #1484; please refresh the description (and "taxonomy" in the title) to match what this PR contains.

---

This review was drafted by an AI-assisted tool and
confirmed by an Apache Magpie maintainer. The findings
below are observations, not blockers; an Apache Magpie
maintainer — a real person — will take the next look at the
PR. If you think a finding is mis-applied, please reply on
the PR and a maintainer will weigh in.

More on how Apache Magpie handles maintainer review:
CONTRIBUTING.md.

[potiuk]

Thanks — all three points from the last review are in (the commented-out guild_id in the template and the contract README, "channel names (Discord also accepts IDs)", and Matrix + Zulip in the contributor-growth spec), and the title and description now match what this PR contains. It's consistent with #1484's current head, so this is ready to land as soon as #1484 does.

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confirmed by an Apache Magpie maintainer. The maintainer
approving this PR has read the findings and signed off. If
something feels off, please reply on the PR and a maintainer
will follow up.

More on how Apache Magpie handles maintainer review:
CONTRIBUTING.md.