fix(hooks): always mine the active transcript as convos, additive to MEMPAL_DIR

#1230 fixed --mode convos for the case where MEMPAL_DIR was unset, but
left two configurations broken:

  - MEMPAL_DIR set to a project dir: convos never mined (MEMPAL_DIR
    overrode the transcript path); only project files were ingested.
  - MEMPAL_DIR set to a conversations dir per the old hooks/README: the
    projects miner ran on JSONL — same wrong-miner behaviour.

The shell hooks (mempal_save_hook.sh, mempal_precompact_hook.sh) had
the same MEMPAL_DIR-overrides-transcript bug AND were missing --mode
on every spawned `mempalace mine` call.

Make the auto-ingest *additive*. _get_mine_dir → _get_mine_targets,
returning a list of (dir, mode) pairs:

  - MEMPAL_DIR (when valid) contributes (dir, "projects")
  - A valid transcript JSONL contributes (parent, "convos")
  - Both can appear together; the hook spawns one ingest per target

Same change applied to the shell save and precompact hooks. Precompact
also gained transcript_path parsing so it can run the convos mine
synchronously before context is compressed. hooks/README.md updated to
describe MEMPAL_DIR as a project-files target, never a convos target.

hooks/mempal_precompact_hook.sh

@@ -41,17 +41,18 @@
 # to save everything. After the AI saves, compaction proceeds normally.
 #
 # === MEMPALACE CLI ===
-# This repo uses: mempalace mine <dir>
-# or:            mempalace mine <dir> --mode convos
-# Set MEMPAL_DIR below if you want the hook to auto-ingest before compaction.
-# Leave blank to rely on the AI's own save instructions.
+# The hook ALWAYS mines the active conversation transcript synchronously
+# before compaction (via `mempalace mine <transcript-dir> --mode convos`).
+# MEMPAL_DIR is an *additional*, optional target for project files — it
+# does not replace the conversation mine.
 
 STATE_DIR="$HOME/.mempalace/hook_state"
 mkdir -p "$STATE_DIR"
 
-# Optional: set to the directory you want auto-ingested before compaction.
-# Example: MEMPAL_DIR="$HOME/conversations"
-# Leave empty to skip auto-ingest (AI handles saving via the block reason).
+# Optional: project directory (code / notes / docs) to also mine before
+# compaction. Mined with `--mode projects`. The conversation transcript
+# is always mined regardless — this is purely additive.
+# Example: MEMPAL_DIR="$HOME/projects/my_app"
 MEMPAL_DIR=""
 
 # Resolve the Python interpreter. Same contract as mempal_save_hook.sh:
@@ -64,15 +65,34 @@ fi
 # Read JSON input from stdin
 INPUT=$(cat)
 
-SESSION_ID=$(echo "$INPUT" | "$MEMPAL_PYTHON_BIN" -c "import sys,json; print(json.load(sys.stdin).get('session_id','unknown'))" 2>/dev/null)
+# Parse session_id and transcript_path in one call. Sanitize both before
+# interpolating into shell — same contract as mempal_save_hook.sh.
+eval $(echo "$INPUT" | "$MEMPAL_PYTHON_BIN" -c "
+import sys, json, re
+data = json.load(sys.stdin)
+sid = data.get('session_id', 'unknown')
+tp = data.get('transcript_path', '')
+safe = lambda s: re.sub(r'[^a-zA-Z0-9_/.\-~]', '', str(s))
+print(f'SESSION_ID=\"{safe(sid)}\"')
+print(f'TRANSCRIPT_PATH=\"{safe(tp)}\"')
+" 2>/dev/null)
+
+# Expand ~ in path
+TRANSCRIPT_PATH="${TRANSCRIPT_PATH/#\~/$HOME}"
 
 echo "[$(date '+%H:%M:%S')] PRE-COMPACT triggered for session $SESSION_ID" >> "$STATE_DIR/hook.log"
 
-# Optional: run mempalace ingest synchronously so memories land before compaction
+# Run ingest synchronously so memories land before compaction. Two
+# independent targets — both run if both are set:
+#   1. TRANSCRIPT_PATH (from Claude Code) → parent dir, --mode convos
+#   2. MEMPAL_DIR → --mode projects
+if [ -n "$TRANSCRIPT_PATH" ] && [ -f "$TRANSCRIPT_PATH" ]; then
+    mempalace mine "$(dirname "$TRANSCRIPT_PATH")" --mode convos \
+        >> "$STATE_DIR/hook.log" 2>&1
+fi
 if [ -n "$MEMPAL_DIR" ] && [ -d "$MEMPAL_DIR" ]; then
-    SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
-    REPO_DIR="$(dirname "$SCRIPT_DIR")"
-    mempalace mine "$MEMPAL_DIR" >> "$STATE_DIR/hook.log" 2>&1
+    mempalace mine "$MEMPAL_DIR" --mode projects \
+        >> "$STATE_DIR/hook.log" 2>&1
 fi
 
 # Silent: return empty JSON to not block. "decision": "allow" is invalid —