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.

INBOX.md

@@ -0,0 +1,33 @@
+# Inbox — cross-project capture buffer
+
+Raw, untriaged ideas and bugs for **any** repo, captured from anywhere so they stop
+scattering into phone notes. `/capture` appends here; `/triage`, run inside a project,
+drains that project's items into its `AGENTS.md` (`## Current state`) or `ROADMAP.md`. This
+buffer is upstream of every repo's ROADMAP — nothing here is owned or scheduled until
+triaged.
+
+**Line format** — one item per line:
+
+```
+- [ ] (project) [type][Pn] note — optional context, YYYY-MM-DD
+```
+
+- `project` — the target repo's folder name (e.g. `relay`), or `standards` for this repo,
+  or `?` if unsure. For an idea that would be a **brand-new repo** (no folder exists yet),
+  use `new` — or `new:working-name` if you have a name in mind.
+- `type` — `bug` | `feature` | `idea` | `skill` | `agent` | `project` | `chore`
+  (`project` = a potential new repo; handled by the new-repo bootstrap, not `/triage`).
+- `Pn` — priority `P0` (drop-everything) … `P3` (someday). Default `P2` if unspecified.
+- `[ ]` unchecked = untriaged; `/triage` removes items once they're routed.
+
+Example:
+
+```
+- [ ] (relay) [bug][P1] health-check probes the wrong port after the bind refactor — found while testing, 2026-06-14
+```
+
+---
+
+## Items
+
+<!-- /capture appends below this line -->