feat(plugin): a directory says which project it belongs to, git repo or not (#4085)

All six hooks scoped their requests one way: `git remote get-url origin`,
resolved server-side through the repo bindings. That key does not exist
outside a git repo, so a session in a plain directory was unscoped in every
hook at once — no project context, no prior-art scoping, no project rules —
and silently, because a missing remote is indistinguishable from a remote
nobody bound.

A `.scribe` file is the second key, read by the shared scribe_scope_query so a
directory scopes the same way everywhere:

    {"instance": "https://scribe.example.com", "project_id": 2, "project": "…"}

`instance` is why the file is not just a number: an id is a different project
on every Scribe, so a marker that travels — a copied directory, a shared
machine, a repo someone else clones — would otherwise scope the session to the
wrong project without a word. Compared host-only, and a mismatch drops the id:
no project beats the wrong project. A bare integer is accepted too, since it
is what a person writes by hand. The marker beats a git remote — someone put
the file there on purpose — which is also how a directory overrides its
binding.

Two things it found on the way:

  * An explicit project_id that did not resolve rendered NO message at all —
    the branch hung off `if project_id` as an `elif`, so a caller holding a
    pointer it believed in got a context that silently omitted the project it
    had asked for. Now reported.
  * The refusal reason was a global set inside a function every caller reads
    through `$( )`. The assignment died with the subshell, leaving the caller
    to read an unset variable under `set -u` — which aborts the hook and costs
    the whole session's SessionStart context, to fetch a warning about a file.
    It comes back through stdout with the id instead, and a test pins it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01821k5B3Ysecp9fNYs92Kuy

plugin/hooks/scribe_autoinject.sh

@@ -65,14 +65,11 @@ q=$(printf '%s' "$prompt" | head -c 2000)
 # worth retrieving against were exactly the ones silently dropped. -s slurps.
 q_enc=$(printf '%s' "$q" | jq -sRr '@uri' 2>/dev/null) || exit 0
 
-# Resolve the working repo's remote so the server can scope to the bound project.
+# Scope to this directory's project — a `.scribe` marker, else the git remote.
 repo_dir=${event_cwd:-${CLAUDE_PROJECT_DIR:-$PWD}}
-repo=$(git -C "$repo_dir" remote get-url origin 2>/dev/null || true)
+scope=$(scribe_scope_query "$repo_dir")
 repo_q=""
-if [ -n "$repo" ]; then
-  enc=$(printf '%s' "$repo" | jq -sRr '@uri' 2>/dev/null) || enc=""
-  [ -n "$enc" ] && repo_q="&repo=${enc}"
-fi
+[ -n "$scope" ] && repo_q="&${scope}"
 
 # Per-session dedup: ids already injected this session are skipped.
 state_dir="${TMPDIR:-/tmp}/scribe-autoinject"