docs: separate the API-only flags from the ones needing a checkout

Two flags in the reference said one thing and did another.

`-o` was listed as a global output-format flag and the Tips section
recommended `-o json` without qualification. On `tea api` it is a file
name: `-o json` writes the body to a file called json and leaves stdout
empty, so the next parse fails with a JSONDecodeError that looks like a
server refusal. Scoped to entity commands, and api's meaning named in
all three places that mention it.

`--repo owner/repo` was documented as a general substitute for standing
in a checkout. For `pulls create`, `pulls checkout` and `pulls clean` it
is not: the slug is rejected with 'local repository required', advice
that reads like the flag was missing. Verified from outside any repo —
those three refuse a slug and accept a path, while pulls list,
milestones, releases and times take the slug from anywhere. All three
working forms are written down, including the git-worktree one (point
--repo at the main checkout) and the api fallback.

Closes #35
Closes #28

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

skills/use/SKILL.md

@@ -58,6 +58,37 @@ The pin takes effect immediately — no restart. Only `tea logins list` and
 per-project by the operator (see `/tea:auth`) and injected by the guard.
 Config lives in `$XDG_CONFIG_HOME/tea`.
 
+### `--repo` takes a slug — except where a checkout is required
+
+A few commands touch local git, not just the API, and for those `--repo`
+**must be a path to a checkout**; a slug is rejected:
+
+```
+Error: local repository required: execute from a repo dir, or specify a path with --repo
+```
+
+The message reads like the flag is missing even when it was passed. Confirmed
+for `pulls create`, `pulls checkout` and `pulls clean` (tea 0.14.x). Everything
+that is only an API call — `pulls list`, `milestones`, `releases`, `times`,
+`labels`, `issues` — takes the slug from any directory.
+
+Three working forms for `pulls create`:
+
+```bash
+# 1. cwd inside the checkout, no --repo at all
+tea pulls create --login "$GITEA_LOGIN" --head feat/x --base main \
+  --title "…" --description "…"
+
+# 2. from anywhere, --repo as a PATH (this is also the git-worktree answer:
+#    point it at the main checkout)
+tea pulls create --login "$GITEA_LOGIN" --repo /path/to/checkout \
+  --head feat/x --base main --title "…" --description "…"
+
+# 3. no checkout in reach — POST it, where owner/repo is a slug again
+tea api --login "$GITEA_LOGIN" -X POST -d @tmp/pull/x.json \
+  repos/{owner}/{repo}/pulls
+```
+
 ## Index
 
 - [tea CLI overview](references/tea/index.md) — global flags, common options, output formats
@@ -125,7 +156,11 @@ are still fine via entity commands. Always the placeholder, never a login name.
 
 ## Tips
 
-- Pass `-o json` for structured output when parsing programmatically.
+- Pass `-o json` for structured output when parsing programmatically — on
+  **entity commands only**. On `tea api`, `-o` is a *file name*: `-o json`
+  writes the response body to a file called `json` and leaves stdout empty.
+  The response is already JSON, so there is nothing to format; use `-` for
+  stdout, or leave the flag off.
 - Use `--fields, -f` to narrow columns.
 - Pagination: `--page, -p <n>` and `--limit, --lm <n>` (defaults 1 / 30).
 - If a `tea` command is blocked by `tea-guard`: either you forgot