fix(plugin): the hooks need no jq and no tac (#4107)

Every hook opened `command -v jq >/dev/null 2>&1 || exit 0`, so on a machine
without jq the operator got no session context, no rules, no prior art and no
process sync — and not one word saying why, because `exit 0` is
indistinguishable from "ran fine, nothing to say". jq is absent by default on
macOS, on the Debian/Ubuntu slim images, on Alpine and in most CI containers.
That is not a prerequisite to document; it is the plugin handing its own
packaging problem to whoever installs it.

`tac` was worse: GNU-only, so the prior-art hook's enclosing-definition arm
did nothing at all on every Mac, silently, from the day it shipped. It is not
replaced but removed — scribe_defs judges each line independently, so
extracting forward and taking `tail -1` is the same answer as reversing and
taking the head, and it drops the early-exit `head` that #4042 was filed for.

No server contract changed, so a lagging plugin cache keeps working.

  scribe_json.awk   JSON -> IDX<TAB>PATH<TAB>VALUE. Two modes: `whole` for an
                    event or a response body, `lines` for a transcript, where
                    an unparseable record is dropped and the rest still read —
                    the `map(try fromjson catch empty)` the jq program opened
                    with. Arrays also report their LENGTH at `[#]`, which is
                    what keeps "zero notes" distinct from "no answer" (#2932).
  scribe_turn.awk   the turn-bounding program, replacing the thirty lines of
                    jq in the Stop hook.
  scribe_defs.sh    scribe_json_flat / _pick / _list / _len / _list_minus read,
                    scribe_json_out writes the envelope (five copies of one
                    shape, gone), scribe_urlenc replaces `jq -sRr '@uri'`.

Percent-encoding goes through `od -tu1` rather than an awk character loop on
purpose: awk's idea of a character follows the locale, so gawk reads an
accented letter as one and mawk as two, and an encoder built on substr() would
emit a different URL depending on which awk is installed. Encoding is defined
on bytes. Verified byte-identical to `jq -sRr '@uri'`.

Measured, not assumed. The per-event path costs 8ms against jq's 3ms. The
transcript path was 70x slower until two fixes: the Stop hook now finds where
the turn starts with a fixed-string grep before parsing (a needle carrying
unescaped quotes cannot occur inside a JSON string, so it matches only at a
record's top level — checked against a full JSON parse of a 27MB transcript:
152 prompt records, 152 matches, no misses, no extras), and the parser reads
each token out of a 1024-byte window instead of copying the rest of the buffer
per token, which was quadratic in line length on the 400KB tool results a
transcript carries.

Differential-tested against the jq program it replaces over 724 windows cut
from three real transcripts — 724 identical, 0 mismatched, 45 of them
exercising a real task close and a real reply. That sweep is what caught
`scribe_turn.awk` never setting FS, which truncated every multi-word reply at
its first space and was invisible to a test whose replies were all empty.

check_plugin.py's `jq -R` lint becomes a guard against either binary coming
back, and three smoke checks lose their `shutil.which("jq")` skip. jq is not
in `ci-python` either, so those three announced a skip on every CI run and had
never once run there: removing the dependency from the product also closed a
permanent hole in its verification. They pass now across all ten hooks.

tests/test_hook_json_reader.py is a differential against Python's `json` over
nested objects, arrays, unicode, escapes, control characters, empty cases and
a value longer than the token window, plus the envelope, the encoder and the
turn analyzer. 139 cases.

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

plugin/hooks/scribe_after_write.sh

@@ -31,7 +31,6 @@
 #   SCRIBE_URL / SCRIBE_TOKEN override for the settings.json dogfooding path.
 set -uo pipefail
 
-command -v jq  >/dev/null 2>&1 || exit 0
 command -v git >/dev/null 2>&1 || exit 0
 
 # shellcheck source=plugin/hooks/scribe_defs.sh
@@ -39,10 +38,11 @@ command -v git >/dev/null 2>&1 || exit 0
 
 # PostToolUse delivers { session_id, cwd, tool_name, tool_input, tool_response }.
 event=$(cat 2>/dev/null || true)
-tool_name=$(printf '%s' "$event" | jq -r '.tool_name // empty' 2>/dev/null) || exit 0
+event_flat=$(printf '%s' "$event" | scribe_json_flat)
+tool_name=$(scribe_json_pick "$event_flat" '.tool_name')
 [ "$tool_name" = "Bash" ] || exit 0
-session_id=$(printf '%s' "$event" | jq -r '.session_id // empty' 2>/dev/null) || session_id=""
-event_cwd=$(printf '%s' "$event" | jq -r '.cwd // empty' 2>/dev/null) || event_cwd=""
+session_id=$(scribe_json_pick "$event_flat" '.session_id')
+event_cwd=$(scribe_json_pick "$event_flat" '.cwd')
 work_dir=${event_cwd:-${CLAUDE_PROJECT_DIR:-$PWD}}
 repo_root=$(git -C "$work_dir" rev-parse --show-toplevel 2>/dev/null) || exit 0
 [ -n "$repo_root" ] || exit 0
@@ -153,12 +153,12 @@ while IFS= read -r rel_path; do
   unreached_context=""
   if [ -n "$url" ] && [ -n "$token" ]; then
     q=$(printf '%s' "$code" | head -c 1200)
-    path_enc=$(printf '%s' "$rel_path" | jq -sRr '@uri' 2>/dev/null) || path_enc=""
-    code_enc=$(printf '%s' "$q" | jq -sRr '@uri' 2>/dev/null) || code_enc=""
+    path_enc=$(printf '%s' "$rel_path" | scribe_urlenc) || path_enc=""
+    code_enc=$(printf '%s' "$q" | scribe_urlenc) || code_enc=""
     shapes_q=""
     enc=$(printf '%s\n' "$names" \
       | awk -F'\t' 'NF>=2 {printf "%s%s:%s", (n++?",":""), $1, $2}' \
-      | jq -sRr '@uri' 2>/dev/null) || enc=""
+      | scribe_urlenc) || enc=""
     [ -n "$enc" ] && shapes_q="&shapes=${enc}"
     exclude_q=""; sync_exclude_q=""; derive_exclude_q=""
     if [ -f "$idfile" ]; then
@@ -170,7 +170,7 @@ while IFS= read -r rel_path; do
       [ -n "$sync_seen" ] && sync_exclude_q="&exclude_sync_ids=${sync_seen}"
     fi
     if [ -f "$derivefile" ]; then
-      derive_seen=$(tr '\n' ',' < "$derivefile" 2>/dev/null | sed 's/,$//' | jq -sRr '@uri' 2>/dev/null) || derive_seen=""
+      derive_seen=$(tr '\n' ',' < "$derivefile" 2>/dev/null | sed 's/,$//' | scribe_urlenc) || derive_seen=""
       [ -n "$derive_seen" ] && derive_exclude_q="&exclude_derive=${derive_seen}"
     fi
     # The rules marker is gone with the resident set it aged (milestone 394).
@@ -197,12 +197,14 @@ while IFS= read -r rel_path; do
         unreached_context=$(scribe_unreached "$state_dir" "$safe_sid" 8 "$rel_path")
       fi
     fi
+    body_flat=""
     if [ -n "$body" ]; then
-      context=$(printf '%s' "$body" | jq -r '.context // empty' 2>/dev/null) || context=""
+      body_flat=$(printf '%s' "$body" | scribe_json_flat)
+      context=$(scribe_json_pick "$body_flat" '.context')
       if [ -n "$context" ]; then
-        printf '%s' "$body" | jq -r '((.note_ids // []) - (.sync_note_ids // []))[]?' 2>/dev/null >> "$idfile" || true
-        printf '%s' "$body" | jq -r '(.sync_note_ids // [])[]?' 2>/dev/null >> "$syncfile" || true
-        printf '%s' "$body" | jq -r '(.derive_keys // [])[]?' 2>/dev/null >> "$derivefile" || true
+        scribe_json_list_minus "$body_flat" '.note_ids' '.sync_note_ids' >> "$idfile" || true
+        scribe_json_list "$body_flat" '.sync_note_ids' >> "$syncfile" || true
+        scribe_json_list "$body_flat" '.derive_keys' >> "$derivefile" || true
         # Several files in one call may name the same family: keep each
         # token once, so the next request's exclude list stays exact.
         for f in "$idfile" "$syncfile" "$derivefile"; do
@@ -217,7 +219,7 @@ while IFS= read -r rel_path; do
   # call that did not answer; "nothing recorded" is a claim only an answer
   # can back.
   if [ -n "$local_lines" ] && [ "$reached" != 0 ]; then
-    n_recorded=$(printf '%s' "$body" | jq -r '.note_ids | length' 2>/dev/null) || n_recorded=0
+    n_recorded=$(scribe_json_len "$body_flat" '.note_ids')
     if [ "${n_recorded:-0}" = "0" ] || [ "$n_recorded" = "" ]; then
       local_context="${local_context}"$'\n'"> None of those existing copies is recorded in Scribe. If the version just written is the canonical one — or this edit is consolidating the copies — record it now with create_snippet so the next session is offered it instead of writing another copy."
     fi
@@ -238,6 +240,5 @@ while IFS= read -r rel_path; do
 done <<< "$changed"
 
 [ -n "$combined" ] || exit 0
-jq -n --arg c "$combined" \
-  '{hookSpecificOutput: {hookEventName: "PostToolUse", additionalContext: $c}}'
+scribe_json_out PostToolUse "$combined"
 exit 0