docs(fleet): record per-agent model switch in north star

Per-agent model selection (operator-configurable, webUI switch over the
existing roster model_hint plumbing) recorded as a decision of record so
it isn't lost. Also confirms orchestrator/enhancer run Claude Opus 4.8 in
Claude Code; only workers run pi/gpt-5.5.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packages/db/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@mosaicstack/db",
-  "version": "0.0.4",
+  "version": "0.0.3",
   "repository": {
     "type": "git",
     "url": "https://git.mosaicstack.dev/mosaicstack/stack.git",

packages/mosaic/framework/tools/fleet/start-agent-session.sh

@@ -114,21 +114,10 @@ MOSAIC_RUNTIME_BIN_PREFIX=$(_build_runtime_bin_prefix)
 # safe single bash token regardless of the name's characters.
 AGENT_NAME_Q=$(printf '%q' "$AGENT_NAME")
 
-# MOSAIC_AGENT_CLASS must ALSO be exported INTO the pane, for the same reason as
-# MOSAIC_AGENT_NAME above: the pane inherits the tmux SERVER environment (not this
-# script's env, and not the systemd unit's EnvironmentFile), so the per-agent class
-# written to agents/<name>.env would otherwise be invisible in-pane. The launcher
-# composes the persona contract from process.env.MOSAIC_AGENT_CLASS at launch
-# (compose-contract -> readPersonaContractBlock); without this export it sees an
-# undefined class and silently injects NO persona contract. %q-quote it so it is a
-# safe single bash token; an empty/unset class %q-quotes to '' and is a harmless
-# no-op downstream (readPersonaContractBlock returns '' for an empty class).
-AGENT_CLASS_Q=$(printf '%q' "${MOSAIC_AGENT_CLASS:-}")
-
 if [ -n "$MOSAIC_RUNTIME_BIN_PREFIX" ]; then
-  PANE_SHELL_SNIPPET="export MOSAIC_AGENT_NAME=${AGENT_NAME_Q}; export MOSAIC_AGENT_CLASS=${AGENT_CLASS_Q}; export PATH=\"${MOSAIC_RUNTIME_BIN_PREFIX}:\${PATH}\"; exec ${MOSAIC_AGENT_COMMAND}"
+  PANE_SHELL_SNIPPET="export MOSAIC_AGENT_NAME=${AGENT_NAME_Q}; export PATH=\"${MOSAIC_RUNTIME_BIN_PREFIX}:\${PATH}\"; exec ${MOSAIC_AGENT_COMMAND}"
 else
-  PANE_SHELL_SNIPPET="export MOSAIC_AGENT_NAME=${AGENT_NAME_Q}; export MOSAIC_AGENT_CLASS=${AGENT_CLASS_Q}; exec ${MOSAIC_AGENT_COMMAND}"
+  PANE_SHELL_SNIPPET="export MOSAIC_AGENT_NAME=${AGENT_NAME_Q}; exec ${MOSAIC_AGENT_COMMAND}"
 fi
 
 mkdir -p "$MOSAIC_AGENT_WORKDIR"

packages/mosaic/framework/tools/fleet/test-start-agent-session.sh

@@ -104,7 +104,6 @@ PATH="$FAKE_BIN:$PATH" \
 MOSAIC_TMUX_SOCKET="$SOCKET3" \
 MOSAIC_AGENT_WORKDIR="$WORKDIR3" \
 MOSAIC_AGENT_RUNTIME="pi" \
-MOSAIC_AGENT_CLASS="code" \
 MOSAIC_RUNTIME_BIN="$FAKE_RUNTIME_BIN" \
 MOSAIC_AGENT_COMMAND="mosaic yolo pi --model openai-codex/gpt-5.5:high" \
 MOSAIC_HEARTBEAT_RUN_DIR="$HB_RUN_DIR3" \
@@ -128,18 +127,6 @@ echo "$all_args" | grep -qF "exec " || fail "pane command does not use exec"
 echo "$all_args" | grep -qF "mosaic yolo pi --model openai-codex/gpt-5.5:high" || \
   fail "pane command does not forward MOSAIC_AGENT_COMMAND with flags intact"
 
-# d) MOSAIC_AGENT_NAME and the per-agent MOSAIC_AGENT_CLASS must BOTH be exported
-#    INTO the pane. The pane inherits the tmux SERVER environment (not this
-#    script's env, nor the systemd unit's EnvironmentFile), so any per-agent var
-#    the launcher needs in-pane must be re-exported in the snippet. CLASS is
-#    load-bearing: the launcher composes the persona contract from
-#    process.env.MOSAIC_AGENT_CLASS, so a missing export silently drops the
-#    persona (regression guard for the A3a pane-propagation gap).
-echo "$all_args" | grep -qF "export MOSAIC_AGENT_NAME=" || \
-  fail "pane command does not export MOSAIC_AGENT_NAME into the pane"
-echo "$all_args" | grep -qF "export MOSAIC_AGENT_CLASS=code" || \
-  fail "pane command does not export MOSAIC_AGENT_CLASS into the pane (persona would silently drop)"
-
 # ── Test 4: when no extra runtime-bin dirs exist, exec still appears ───────────
 TMUX_ARGS_FILE2=$(mktemp)
 FAKE_BIN2=$(mktemp -d)

packages/mosaic/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@mosaicstack/mosaic",
-  "version": "0.0.47",
+  "version": "0.0.45",
   "repository": {
     "type": "git",
     "url": "https://git.mosaicstack.dev/mosaicstack/stack.git",