refactor: Clean up Cargo dependencies - remove unused, update outdated

- Remove unused const_format from g3-planner (never imported)
- Remove unused thiserror from workspace and 5 crates (declared but never used)
- Update termimad 0.31 -> 0.34 in studio (consistency with g3-cli)
- Update indicatif 0.17 -> 0.18 in g3-cli
- Update ratatui 0.29 -> 0.30 in g3-cli
- Update walkdir 2.4 -> 2.5 in g3-core
- Update image 0.24 -> 0.25 in g3-computer-control (macOS + Linux)
- Update config 0.14 -> 0.15 in workspace

Blocked: reqwest 0.11 -> 0.12/0.13 requires breaking API changes to
bytes_stream() used in 4 providers - needs separate migration effort.

All tests pass. No behavior changes.

Agent: fowler

crates/g3-cli/Cargo.toml

@@ -23,10 +23,10 @@ dirs = "5.0"
 tokio-util = "0.7"
 sha2 = "0.10"
 hex = "0.4"
-indicatif = "0.17"
+indicatif = "0.18"
 chrono = { version = "0.4", features = ["serde"] }
 crossterm = "0.29.0"
-ratatui = "0.29"
+ratatui = "0.30"
 termimad = "0.34.0"
 regex = "1.10"
 syntect = "5.3"

crates/g3-computer-control/Cargo.toml

@@ -10,7 +10,6 @@ edition = "2021"
 # Workspace dependencies
 tokio = { workspace = true }
 anyhow = { workspace = true }
-thiserror = { workspace = true }
 serde = { workspace = true }
 serde_json = { workspace = true }
 tracing = { workspace = true }
@@ -31,12 +30,12 @@ core-foundation = "0.10"
 cocoa = "0.25"
 objc = "0.2"
 accessibility = "0.2"
-image = "0.24"
+image = "0.25"
 
 # Linux dependencies
 [target.'cfg(target_os = "linux")'.dependencies]
 x11 = { version = "2.21", features = ["xlib", "xtest"] }
-image = "0.24"
+image = "0.25"
 
 # Windows dependencies
 [target.'cfg(target_os = "windows")'.dependencies]

crates/g3-config/Cargo.toml

@@ -8,7 +8,6 @@ description = "Configuration management for G3 AI coding agent"
 config = { workspace = true }
 serde = { workspace = true }
 anyhow = { workspace = true }
-thiserror = { workspace = true }
 toml = "0.8"
 shellexpand = "3.0"
 dirs = "5.0"

crates/g3-core/Cargo.toml

@@ -15,7 +15,6 @@ g3-computer-control = { path = "../g3-computer-control" }
 tokio = { workspace = true }
 reqwest = { workspace = true }
 anyhow = { workspace = true }
-thiserror = { workspace = true }
 tracing = { workspace = true }
 serde = { workspace = true }
 serde_json = { workspace = true }
@@ -45,7 +44,7 @@ tree-sitter-haskell = { git = "https://github.com/tree-sitter/tree-sitter-haskel
 tree-sitter-scheme = "0.24"
 tree-sitter-racket = "0.24"
 streaming-iterator = "0.1"
-walkdir = "2.4"
+walkdir = "2.5"
 
 # Datalog engine for invariant verification
 datafrog = "2.0.1"

crates/g3-execution/Cargo.toml

@@ -8,7 +8,6 @@ description = "Code execution engine for G3 AI agent"
 tokio = { workspace = true }
 anyhow = { workspace = true }
 futures = "0.3"
-thiserror = { workspace = true }
 tracing = { workspace = true }
 regex = "1.0"
 tempfile = "3.0"

crates/g3-planner/Cargo.toml

@@ -10,7 +10,6 @@ g3-core = { path = "../g3-core" }
 g3-config = { path = "../g3-config" }
 serde = { workspace = true }
 serde_json = { workspace = true }
-const_format = "0.2"
 anyhow = { workspace = true }
 tokio = { workspace = true }
 chrono = { version = "0.4", features = ["serde"] }

crates/g3-providers/Cargo.toml

@@ -8,7 +8,6 @@ description = "LLM provider abstractions for G3 AI coding agent"
 tokio = { workspace = true }
 reqwest = { workspace = true }
 anyhow = { workspace = true }
-thiserror = { workspace = true }
 serde = { workspace = true }
 serde_json = { workspace = true }
 tracing = { workspace = true }

crates/studio/Cargo.toml

@@ -16,7 +16,7 @@ serde = { workspace = true }
 serde_json = { workspace = true }
 uuid = { workspace = true }
 chrono = { version = "0.4", features = ["serde"] }
-termimad = "0.31"
+termimad = "0.34"
 
 [dev-dependencies]
 tempfile = "3"