Add capture/triage inbox loop; dogfood AGENTS.md/ROADMAP; document git-tracking standard

Introduce the cross-project capture->triage->roadmap loop: /capture appends an
idea or bug to INBOX.md from any repo (new-project ideas included), /triage drains
a project's items into its AGENTS.md or ROADMAP.md. Give the standards repo its own
AGENTS.md (+ CLAUDE.md symlink) and ROADMAP.md so it follows its own standard, and
add a 'What git tracks' section to portability.md plus the canonical .gitignore
block answering what is committed vs gitignored around .claude and symlinks.

adapters/claude/commands/capture.md

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+---
+description: Log an idea or bug to the cross-project inbox (INBOX.md in the standards repo) from any repo, without acting on it
+argument-hint: the idea or bug — optionally name the project, type, and priority
+allowed-tools: Bash(git:*), Read, Edit, Write
+---
+
+Capture a quick note into the cross-project inbox. Do not act on it — just record it
+durably and confirm.
+What to capture (the note, optionally with project / type / priority): $ARGUMENTS
+
+Your complete guide — the fields to parse, the inbox line format, and the commit/push step
+that makes the note durable — is at:
+
+    ~/Projects/standards/guides/capture.md
+
+Read it in full first, then follow it exactly. If you cannot read that file, stop and
+report precisely that — do not improvise the capture or drop the note.

adapters/claude/commands/triage.md

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+---
+description: Drain this project's items from the cross-project inbox (INBOX.md) into its AGENTS.md Current state or ROADMAP.md, with your approval
+argument-hint: [optional focus, e.g. "just the bugs"]
+allowed-tools: Bash(git:*), Read, Edit, Write, Grep, Glob
+---
+
+Triage the cross-project inbox for the repository in the current working directory: route
+this repo's captured items to where they belong, then clear them from the inbox.
+Optional focus from me (may be empty): $ARGUMENTS
+
+Your complete guide — how to select this repo's items, the routing destinations, the
+approval gate, and the two-repo commit — is at:
+
+    ~/Projects/standards/guides/triage.md
+
+Read it in full first, then follow it exactly. If you cannot read that file, stop and
+report precisely that — do not improvise the triage.
+
+Routing decisions are mine: propose a destination for each item and wait for my approval
+before editing any project file or removing anything from the inbox.