refactor(experts): replace brand colors with neutral grayscale palette

Update color field in 15 expert YAML configs to use neutral grayscale
and deep accent tones (gray 400-800, stone, amber, dark blue/green),
consistent with the expertIdentity.ts PALETTE and the project convention
for GitHub-style neutral UI coloring.

configs/experts/allenzhang.yaml

@@ -16,7 +16,7 @@ config:
   collaboration_strategy: "cooperative"
   bound_skills: []
   avatar: "A"
-  color: "#07C160"
+  color: "#1e40af"
   is_lead: false
   task_mode: llm_generate
   prompt:

configs/experts/backend_engineer.yaml

@@ -15,7 +15,7 @@ config:
   collaboration_strategy: "cooperative"
   bound_skills: []
   avatar: "B"
-  color: "#fa8c16"
+  color: "#155e75"
   is_lead: false
   task_mode: llm_generate
   prompt:

configs/experts/charlie_munger.yaml

@@ -16,7 +16,7 @@ config:
   collaboration_strategy: "cooperative"
   bound_skills: []
   avatar: "C"
-  color: "#2C3E50"
+  color: "#166534"
   is_lead: false
   task_mode: llm_generate
   prompt:

configs/experts/code_reviewer.yaml

@@ -15,7 +15,7 @@ config:
   collaboration_strategy: "cooperative"
   bound_skills: []
   avatar: "C"
-  color: "#722ed1"
+  color: "#1f2937"
   is_lead: false
   task_mode: llm_generate
   prompt:

configs/experts/dev_team.yaml

@@ -18,7 +18,7 @@ config:
     - qa_engineer
     - code_reviewer
   avatar: "D"
-  color: "#1890ff"
+  color: "#6b7280"
   is_lead: false
   task_mode: llm_generate
   prompt:

configs/experts/elon_musk.yaml

@@ -15,7 +15,7 @@ config:
   collaboration_strategy: "cooperative"
   bound_skills: []
   avatar: "E"
-  color: "#E31937"
+  color: "#9ca3af"
   is_lead: false
   task_mode: llm_generate
   prompt:

configs/experts/frontend_engineer.yaml

@@ -15,7 +15,7 @@ config:
   collaboration_strategy: "cooperative"
   bound_skills: []
   avatar: "F"
-  color: "#52c41a"
+  color: "#1e40af"
   is_lead: false
   task_mode: llm_generate
   prompt:

configs/experts/jeff_bezos.yaml

@@ -16,7 +16,7 @@ config:
   collaboration_strategy: "cooperative"
   bound_skills: []
   avatar: "J"
-  color: "#FF9900"
+  color: "#92400e"
   is_lead: false
   task_mode: llm_generate
   prompt:

configs/experts/paul_graham.yaml

@@ -17,7 +17,7 @@ config:
   collaboration_strategy: "cooperative"
   bound_skills: []
   avatar: "P"
-  color: "#FF6600"
+  color: "#92400e"
   is_lead: false
   task_mode: llm_generate
   prompt:

configs/experts/private_board.yaml

@@ -18,7 +18,7 @@ config:
     - charlie_munger
     - paul_graham
   avatar: "P"
-  color: "#8E44AD"
+  color: "#7c2d12"
   is_lead: false
   task_mode: llm_generate
   prompt:

configs/experts/qa_engineer.yaml

@@ -15,7 +15,7 @@ config:
   collaboration_strategy: "cooperative"
   bound_skills: []
   avatar: "Q"
-  color: "#eb2f96"
+  color: "#374151"
   is_lead: false
   task_mode: llm_generate
   prompt:

configs/experts/ray_dalio.yaml

@@ -17,7 +17,7 @@ config:
   collaboration_strategy: "cooperative"
   bound_skills: []
   avatar: "R"
-  color: "#1A5276"
+  color: "#6b7280"
   is_lead: false
   task_mode: llm_generate
   prompt:

configs/experts/steve_jobs.yaml

@@ -17,7 +17,7 @@ config:
   collaboration_strategy: "cooperative"
   bound_skills: []
   avatar: "S"
-  color: "#555555"
+  color: "#1e40af"
   is_lead: false
   task_mode: llm_generate
   prompt:

configs/experts/tech_lead.yaml

@@ -15,7 +15,7 @@ config:
   collaboration_strategy: "cooperative"
   bound_skills: []
   avatar: "T"
-  color: "#1890ff"
+  color: "#92400e"
   is_lead: true
   task_mode: llm_generate
   prompt:

configs/experts/warren_buffett.yaml

@@ -17,7 +17,7 @@ config:
   collaboration_strategy: "cooperative"
   bound_skills: []
   avatar: "W"
-  color: "#1E8449"
+  color: "#78716c"
   is_lead: false
   task_mode: llm_generate
   prompt: