fix(install,uninstall): correct Claude Code hooks schema for SessionStart entry

Regression caught when opening a fresh Claude Code session post-
install.sh: settings.json failed validation with

    hooks > SessionStart > 1 > hooks: Expected array, but received undefined

Root cause: my jq merge appended a flat `{"command": "..."}` entry,
but the Claude Code hook schema is `{matcher?, hooks: [{type, command,
async?}, ...]}` — each SessionStart entry must carry a `hooks` array.

Fixes:
- install.sh — merges a correctly-shaped entry:
    {"hooks": [{"type": "command", "command": "python3 ~/.claude/hooks/prewarm-direct-wrappers.py"}]}
  Idempotency re-checked via flat-scanning all existing entries'
  `hooks[].command` for our exact string; skips append if found.
- uninstall.sh — filters our command out of each entry's `hooks`
  array, then drops entries that become empty. Unrelated SessionStart
  entries (other tools' hooks bundled into separate entries) preserved.
- install.sh also gained `CLAUDE="${CLAUDE:-$HOME/.claude}"` env
  override to match uninstall.sh (enables dry-run testing against a
  scratch settings file) and switched `mktemp` to `mktemp
  "${TMPDIR:-/tmp}/install.XXXXXX"` so the atomic-swap works under
  sandboxes that override $TMPDIR.

Verified dry-run against scratch settings.json with an existing
SessionStart entry:
  - install.sh run 1: appends our entry → 2 entries total.
  - install.sh run 2 (idempotency): still 2 entries.
  - uninstall.sh: strips our entry → back to 1 entry (the pre-
    existing one untouched).

Users who already ran the broken install.sh can either run
uninstall.sh then install.sh again, or manually replace the flat
entry in ~/.claude/settings.json's hooks.SessionStart[] with the
correctly-shaped object.

Author: Blanquitoh

scripts/install.sh

@@ -6,7 +6,8 @@
 set -euo pipefail
 
 REPO="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
-CLAUDE="$HOME/.claude"
+# CLAUDE defaults to ~/.claude; override for dry-runs (CLAUDE=/tmp/foo install.sh).
+CLAUDE="${CLAUDE:-$HOME/.claude}"
 
 # bin files (wrappers + coordinators + shared harness modules)
 BIN_FILES=(
@@ -121,7 +122,7 @@ SETTINGS="$CLAUDE/settings.json"
 if [ -f "$SETTINGS" ]; then
   log "merging permissions + sandbox into $SETTINGS"
   cp "$SETTINGS" "$SETTINGS.bak-$(date +%s)"
-  TMP="$(mktemp)"
+  TMP="$(mktemp "${TMPDIR:-/tmp}/install.XXXXXX")"
   jq '
     .permissions.allow = ((.permissions.allow // []) + [
       "Bash(~/.claude/bin/metals-direct *)",
@@ -155,9 +156,17 @@ if [ -f "$SETTINGS" ]; then
       "~/.coursier/**",
       "/private/var/folders/**/.scala-build/**"
     ] | unique)
-    | .hooks.SessionStart = ((.hooks.SessionStart // []) + [{
-        "command": "python3 ~/.claude/hooks/prewarm-direct-wrappers.py"
-      }] | unique_by(.command))
+    | .hooks.SessionStart = (
+        # append only if our command isnt already registered under any existing entrys hooks array.
+        # Claude Code hook schema: each SessionStart entry is {matcher?, hooks: [{type, command, async?}, ...]}
+        if ((.hooks.SessionStart // []) | map(.hooks // []) | flatten | map(.command) | index("python3 ~/.claude/hooks/prewarm-direct-wrappers.py")) then
+          (.hooks.SessionStart // [])
+        else
+          (.hooks.SessionStart // []) + [{
+            "hooks": [{"type": "command", "command": "python3 ~/.claude/hooks/prewarm-direct-wrappers.py"}]
+          }]
+        end
+      )
   ' "$SETTINGS" > "$TMP" && mv "$TMP" "$SETTINGS"
   log "  merged (backup at $SETTINGS.bak-<ts>)"
 else

scripts/uninstall.sh

@@ -86,7 +86,17 @@ if [ -f "$SETTINGS" ] && command -v jq >/dev/null; then
       "~/.coursier/**",
       "/private/var/folders/**/.scala-build/**"
     ])
-    | .hooks.SessionStart = ((.hooks.SessionStart // []) | map(select(.command != "python3 ~/.claude/hooks/prewarm-direct-wrappers.py")))
+    | .hooks.SessionStart = (
+        # Remove any SessionStart entry whose hooks[].command references our prewarm script.
+        # Also drop entries that become empty after the filter.
+        (.hooks.SessionStart // [])
+        | map(
+            if type == "object" and has("hooks") then
+              .hooks |= map(select(.command != "python3 ~/.claude/hooks/prewarm-direct-wrappers.py"))
+            else . end
+          )
+        | map(select(type != "object" or (.hooks // []) != []))
+      )
   ' "$SETTINGS" > "$TMP" && mv "$TMP" "$SETTINGS"
 fi