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.

guides/capture.md

@@ -0,0 +1,56 @@
+# Capture — append an idea or bug to the cross-project inbox
+
+The user has a thought about some project — a feature, an idea, a bug they just hit — and
+wants it logged *now*, without acting on it and without stopping to decide where it
+belongs. Your whole job is to record it durably and get out of the way. Capture is
+deliberately dumb and uniform: no routing, no triage, no discussion of the merits. Routing
+happens later, via `/triage`, inside the relevant project.
+
+The inbox is a single file: `~/Projects/standards/INBOX.md`. You append to it regardless of
+which repo the user invoked you from.
+
+## Procedure
+
+1. **Parse the note** from the user's input (`$ARGUMENTS`). Extract or infer four fields —
+   keep it fast, ask only when a field is genuinely missing and can't be inferred:
+   - **project** — the target repo. If the user named one, use it. If not, infer from the
+     current working directory's folder name. If you truly can't tell, use `?` (triage will
+     sort it) rather than interrogating the user. If the idea is for a **brand-new repo that
+     doesn't exist yet** ("new project/app/idea for…"), use `new` — or `new:working-name` if
+     they gave a name — and set type `project`. These wait for the new-repo bootstrap flow
+     and are never triaged into an existing repo.
+   - **type** — one of `bug | feature | idea | skill | agent | project | chore` (`project`
+     = a potential new repo, used with a `new`/`new:name` project tag). Infer from wording
+     ("found a bug" → bug, "we should add" → feature, "what if" → idea). Default `idea`.
+   - **priority** — `P0`…`P3`. Use a priority only if the user signals one ("urgent",
+     "P1", "minor"). Default `P2`.
+   - **note** — the user's text, lightly cleaned up to stand on its own later. Preserve
+     their meaning; don't editorialize or expand.
+2. **Append one line** to the `## Items` section of `~/Projects/standards/INBOX.md`, in the
+   exact format the file documents:
+   `- [ ] (project) [type][Pn] note — optional context, YYYY-MM-DD`
+   Use today's date. Don't reformat or reorder existing lines.
+3. **Make it durable.** Commit and push *only the inbox line* so the note survives and is
+   visible from any session or machine — this is the point of the tool, so do it without
+   asking:
+   - `git -C ~/Projects/standards add INBOX.md`
+   - `git -C ~/Projects/standards commit -m "Capture: <short summary>" -- INBOX.md`
+     (the `-- INBOX.md` pathspec commits only the inbox, even if other changes happen to be
+     staged in the standards repo — never sweep unrelated work into a capture commit).
+   - `git -C ~/Projects/standards push` (only if a remote is configured; if the push fails,
+     report it but don't treat the capture as lost — it's committed locally).
+   Do not touch or commit anything in the repo the user invoked you from.
+4. **Confirm in one line** — echo back the exact line you wrote and where, e.g.
+   `Logged to inbox: (relay) [bug][P1] … — triage it next time you're in relay with /triage.`
+   Nothing more; the user is mid-thought on something else.
+
+## Rules
+
+- One invocation = one item, unless the user clearly lists several; then append one line
+  each.
+- Never act on the captured item, open files in the target repo, or start discussing the
+  fix. Capture only.
+- No secrets in the note — if the user's text contains a key/token/password, replace it
+  with a placeholder and say you did.
+- If you cannot write to `~/Projects/standards/INBOX.md` (missing, unwritable), stop and
+  report precisely that — do not silently drop the note or stash it somewhere else.