feat(agents): agent seats - per-agent SOUL, role, definitions dir (#36)

- agents/<name>/ holds agent.json (strictly validated: version, name,
  role?, capabilities?, workspace?, session?) + SOUL.md (persona prose)
- agent.sh: definition loading (quote-safe node defaults file), runtime
  SOUL copy to dataRoot/agents/<name>/, MOSAIC_AGENT_SOUL_FILE ->
  loader fills the SOUL slot from the seat's persona (contract SOUL =
  default persona; governance never overridden)
- seat.json written once at instantiation (seatVersion, name, role, at)
- identity section gains agent role; compose passthrough for role+SOUL
- live user context (M14) + seat SOUL compose the full persona:
  governance -> persona -> identity -> user -> mission
- RELEASE -> 0.0.10; packaged and health-gated activated
- example seat committed: agents/researcher

Closes #36

src/load-contracts.sh

@@ -1,14 +1,33 @@
 #!/bin/sh
-# Load the four immutable contract files in fixed order and write the
-# generated system prompt to /var/lib/mosaic/system-prompt.md.
+# Load agent context and write the generated system prompt to
+# /var/lib/mosaic/system-prompt.md.
 #
-# Order is normative: CONSTITUTION.md, STANDARDS.md, SOUL.md, USER.md.
+# Layers, in normative order:
+#   1. Immutable contracts (image): CONSTITUTION, STANDARDS, SOUL
+#   2. Agent identity (when the launcher names the agent)
+#   3. Mission (when the task/launcher provides one)
+#   4. Live user context (M14): <dataRoot>/user/*.md - user-owned,
+#      dispatched to every launch without rebuilds
 set -eu
 
 CONTRACT_DIR="${1:-/opt/mosaic/contracts}"
 OUT="${2:-/var/lib/mosaic/system-prompt.md}"
 
-FILES="CONSTITUTION.md STANDARDS.md SOUL.md USER.md"
+FILES="CONSTITUTION.md STANDARDS.md"
+
+# SOUL slot (M15): the contract SOUL.md is the DEFAULT persona; a launched
+# agent seat overrides it with its own runtime SOUL (governance contracts
+# are never overridden).
+SOUL_SRC="$CONTRACT_DIR/SOUL.md"
+SOUL_HEADER="SOUL.md"
+if [ -n "${MOSAIC_AGENT_SOUL_FILE:-}" ]; then
+    if [ ! -r "$MOSAIC_AGENT_SOUL_FILE" ]; then
+        echo "load-contracts: agent SOUL not readable: $MOSAIC_AGENT_SOUL_FILE" >&2
+        exit 1
+    fi
+    SOUL_SRC="$MOSAIC_AGENT_SOUL_FILE"
+    SOUL_HEADER="SOUL.md (agent seat override)"
+fi
 
 if [ ! -d "$CONTRACT_DIR" ]; then
     echo "load-contracts: contract directory not found: $CONTRACT_DIR" >&2
@@ -33,14 +52,30 @@ for f in $FILES; do
     printf '\n' >> "$TEMP"
 done
 
+printf '===== CONTRACT: %s =====\n' "$SOUL_HEADER" >> "$TEMP"
+cat "$SOUL_SRC" >> "$TEMP"
+printf '\n' >> "$TEMP"
+
 # Agent identity (M13): when the launcher names the agent, the generated
 # prompt states it - SOUL.md provides the persona, this provides the name.
 if [ -n "${MOSAIC_AGENT_NAME:-}" ]; then
     printf '===== AGENT IDENTITY =====\n' >> "$TEMP"
     printf 'agent name: %s\n' "$MOSAIC_AGENT_NAME" >> "$TEMP"
+    [ -n "${MOSAIC_AGENT_ROLE:-}" ] && printf 'agent role: %s\n' "$MOSAIC_AGENT_ROLE" >> "$TEMP"
     printf '\n' >> "$TEMP"
 fi
 
+# Live user context (M14): every *.md in /var/lib/mosaic/user (sorted) is
+# appended - the user owns this layer and edits it without rebuilds.
+USER_DIR="/var/lib/mosaic/user"
+if [ -d "$USER_DIR" ]; then
+    for f in $(ls "$USER_DIR"/*.md 2>/dev/null | sort); do
+        printf '===== USER CONTEXT: %s =====\n' "$(basename "$f")" >> "$TEMP"
+        cat "$f" >> "$TEMP"
+        printf '\n' >> "$TEMP"
+    done
+fi
+
 # Sanctioned mission injection point (M4): when the task runner provides a
 # mission snapshot, its objective and directives are appended AFTER the
 # immutable contracts. Runtime data; never part of the contract fixtures.