docs: record dev container and PR template gotchas in CLAUDE.md (#25)

Four things cost time or caused a mistake during the repository rebuild and
dependency catch-up, none of which were written down.

pnpm install refuses to run in this container without CI=true, and then refuses
again without --no-frozen-lockfile once a manifest has changed. Neither is
guessable from the error text.

Prettier re-pads markdown tables, so editing one cell in the CI table breaks
format:check in a way that looks unrelated to the edit.

A devcontainers bump is the one dependency class CI cannot verify, since nothing
in CI builds the container. The ghcr manifest carries the feature's option
schema, which is enough to check compatibility without a rebuild.

The PR template section names changed in #19, and four PRs were written against
the old ones because CLAUDE.md only said the template is filled in automatically.

Author: unxwn

CLAUDE.md

@@ -50,6 +50,23 @@ pnpm lint     # oxlint
 - When killing dev servers with `pkill -f`, use a self-excluding pattern such as
   `pgrep -f 'Vox[L]ib'`; a plain `-f VoxLib.Api` also matches the shell running
   the command and kills it.
+- `pnpm install` aborts with `ERR_PNPM_ABORTED_REMOVE_MODULES_DIR_NO_TTY` when it
+  decides to purge `node_modules` and has no TTY to ask. Prefix with `CI=true`.
+  Add `--no-frozen-lockfile` when a manifest changed, because `CI=true` also makes
+  frozen-lockfile the default and the install then fails a second time.
+- Prettier owns `CLAUDE.md` and `README.md`, table alignment included. Editing one
+  cell widens the column and `pnpm format:check` fails until
+  `pnpm exec prettier --write <file>` re-pads the whole table.
+- Nothing in CI builds the dev container, so a `devcontainers` dependency bump is
+  unverified by a green PR. Compare the feature's options across versions without
+  a rebuild:
+
+  ```bash
+  TOKEN=$(curl -s "https://ghcr.io/token?scope=repository:devcontainers/features/node:pull&service=ghcr.io" | jq -r .token)
+  curl -s -H "Authorization: Bearer $TOKEN" -H "Accept: application/vnd.oci.image.manifest.v1+json" \
+    https://ghcr.io/v2/devcontainers/features/node/manifests/2.1.0 \
+    | jq -r '.annotations["dev.containers.metadata"]' | jq .options
+  ```
 
 ## What this project is
 
@@ -92,6 +109,11 @@ PR is where CI runs and where the change becomes reviewable later; a commit
 pushed straight to `main` skips both. `.github/pull_request_template.md` is
 filled in automatically.
 
+Fill in the sections that `.github/pull_request_template.md` actually has, and read
+it rather than copying an older PR. They have already changed once, from
+What / Why / How / Checklist to Summary / Changes / Out of scope / Test plan /
+Dependencies.
+
 **Merge by squashing.** A squash merge collapses every commit on the branch into
 a single commit on `main`. It means you can commit as messily as you like while
 working ("wip", "fix typo", "actually fix it") and `main` still reads as one