fix(plugin): every hook's credential + URL encoding was broken

Three defects, each of which independently made a hook a no-op, and all
three failing silently — which is why the whole dynamic side of the plugin
looked "shipped" while doing nothing.

1. Wrong env var case. Claude Code exports userConfig to hooks as
   CLAUDE_PLUGIN_OPTION_<KEY> with the key UPPERCASED. All four hooks read
   CLAUDE_PLUGIN_OPTION_api_endpoint / _api_token, so both values were
   always empty. That killed the SessionStart dynamic tier, process sync,
   prompt auto-inject, and the write-path prior-art trigger at once.

2. jq -rR is line-oriented. `@uri` under -R encodes input LINE BY LINE, so
   a multi-line payload came back as several encoded lines joined by raw
   newlines — an invalid URL, curl fails, hook exits 0 in silence. Now
   -sRr. This one hid behind (1): auto-inject only ever worked for
   single-line prompts, and prior-art (which posts code, always
   multi-line) could never have worked at all.

3. cut -c1-1200 caps each LINE, not the payload, so the prior-art code
   budget wasn't a budget. Now head -c 1200.

Also widens the SessionStart warning: "neither URL nor token arrived" used
to be treated as a benign unconfigured install and stayed quiet. That is
exactly the state defect (1) produced, so the one install state that most
needed a signal was the only one that emitted none. It now says so, and
names the two other features it silently disables.

Verified against the live instance: dynamic rules + project context load,
auto-inject surfaces #2192 on a multi-line prompt, and the write-path
trigger returns the [here] place-arm hit on a multi-line edit with session
dedup suppressing the repeat.

Refs #2198, #2082

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UaYUaouG9jjhATyuxCKrQs

plugin/hooks/scribe_sync_processes.sh

@@ -18,14 +18,16 @@
 # FAIL-OPEN & SILENT: never blocks a session; emits NOTHING on stdout (so it's
 # safe as a second SessionStart hook). On any fetch failure it exits without
 # touching existing stubs — a transient outage must not wipe the user's skills.
-# Config mirrors the context hook (CLAUDE_PLUGIN_OPTION_* / SCRIBE_* override).
+# Config mirrors the context hook: CLAUDE_PLUGIN_OPTION_API_ENDPOINT /
+# CLAUDE_PLUGIN_OPTION_API_TOKEN (userConfig key UPPERCASED by Claude Code — see
+# #2198), with SCRIBE_URL / SCRIBE_TOKEN as the override.
 set -uo pipefail
 
 command -v jq >/dev/null 2>&1 || exit 0
 command -v curl >/dev/null 2>&1 || exit 0
 
-url=${SCRIBE_URL:-${CLAUDE_PLUGIN_OPTION_api_endpoint:-}}
-token=${SCRIBE_TOKEN:-${CLAUDE_PLUGIN_OPTION_api_token:-}}
+url=${SCRIBE_URL:-${CLAUDE_PLUGIN_OPTION_API_ENDPOINT:-}}
+token=${SCRIBE_TOKEN:-${CLAUDE_PLUGIN_OPTION_API_TOKEN:-}}
 # Guard against an unexpanded `${...}` placeholder arriving as a literal.
 case "$url"   in *'${'*) url="" ;; esac
 case "$token" in *'${'*) token="" ;; esac