feat(fleet): update-surviving persona overrides (roles.local layer, resolver, persona CLI) (H4)

Add a PRESERVE-protected persona override layer at <mosaicHome>/fleet/roles.local/
that survives `mosaic update` while baseline fleet/roles/ keeps reseeding.

- fleet-personas.ts: shared class-extraction (single source of truth, DRY with
  fleet-profiles.ts), resolvePersona (override wins, baseline fallback),
  listPersonaClasses (baseline ⊕ override union), personaStatus
  (baseline/overridden/custom), and the `fleet persona list|show|customize` CLI.
- fleet-profiles.ts: roster validation now uses the override-aware union so a
  profile can reference a user-customized or user-ADDED persona; the old
  listPersonaClasses(rolesDir) is kept as a thin delegate to the shared helper.
- install.sh: add fleet/roles.local to PRESERVE_PATHS (AC-NS-7 guarantee).
- specs: override-wins, custom-add, status classification, AC-NS-7
  update-survival simulation, and profile-validation-accepts-custom-persona.

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

packages/mosaic/framework/install.sh

@@ -37,7 +37,14 @@ INSTALL_MODE="${MOSAIC_INSTALL_MODE:-prompt}"
 # packages/mosaic/src/commands/fleet-backlog.ts). Without these, an update
 # wipes the operator's fleet AND their backlog. Glob entries are honored by
 # both the rsync path (`--exclude`) and the glob-aware cp fallback below.
-PRESERVE_PATHS=("CONSTITUTION.md" "AGENTS.md" "SOUL.md" "USER.md" "TOOLS.md" "STANDARDS.md" "memory" "sources" "credentials" "fleet/*.yaml" "fleet/agents" "fleet/run" "fleet/backlog")
+#
+# fleet/roles.local — the persona OVERRIDE layer (H4). Baseline personas in
+# fleet/roles/ are reseeded normally on every update (delivering new baseline
+# personas), so any local edit there would be clobbered. User customizations
+# and user-ADDED personas instead live in fleet/roles.local/ and MUST survive
+# `mosaic update` — they win over the baseline on merge (AC-NS-7; see
+# packages/mosaic/src/commands/fleet-personas.ts).
+PRESERVE_PATHS=("CONSTITUTION.md" "AGENTS.md" "SOUL.md" "USER.md" "TOOLS.md" "STANDARDS.md" "memory" "sources" "credentials" "fleet/*.yaml" "fleet/agents" "fleet/run" "fleet/backlog" "fleet/roles.local")
 
 # Framework-owned contract files: re-copied from defaults/ on every upgrade (the
 # user must not edit them; a divergent copy is backed up once before overwrite).