feat: add colorgrad, transcript parser, terminal palette detection, and expanded color/input systems

Infrastructure layer for the TUI visual overhaul. Introduces foundational
modules and capabilities that the section-level features build on:

colorgrad (0.7) dependency:
  OKLab gradient interpolation for per-character color transitions in
  sparklines and context bars. Adds ~100K to binary (929K -> 1.0M).

color.rs expansion:
  - parse_hex(): #RRGGBB and #RGB -> (u8, u8, u8) conversion
  - fg_rgb()/bg_rgb(): 24-bit true-color ANSI escape generation
  - gradient_fg(): two-point interpolation via colorgrad
  - make_gradient()/sample_fg(): multi-stop gradient construction and sampling
  - resolve_color() now supports: hex (#FF6B35), bg:color, bg:#hex,
    italic, underline, strikethrough, and palette refs (p:success)
  - Named background constants (BG_RED through BG_WHITE)

transcript.rs (new module):
  Parses Claude Code transcript JSONL files to derive tool use counts,
  turn counts, and per-tool breakdowns. Claude Code doesn't include
  total_tool_uses or total_turns in its JSON — we compute them by scanning
  the transcript. Includes compact cache serialization format and
  skip_lines support for /clear offset handling.

terminal.rs (new module):
  Auto-detects the terminal's ANSI color palette for theme-aware tool
  coloring. Priority chain: WezTerm config > Kitty config > Alacritty
  config > OSC 4 escape sequence query. Parses Lua (WezTerm), key-value
  (Kitty), and TOML/YAML (Alacritty) config formats. OSC 4 queries
  use raw /dev/tty I/O with termios to avoid pipe interference. Includes
  cache serialization helpers for 1-hour TTL caching.

input.rs updates:
  - All structs now derive Serialize (for --dump-state diagnostics)
  - New fields: transcript_path, session_id, cwd, vim.mode, agent.name,
    exceeds_200k_tokens, cost.total_api_duration_ms
  - CurrentUsage: added input_tokens and output_tokens fields
  - #[serde(flatten)] extras on InputData and CostInfo for forward compat

cache.rs:
  Added flush_prefix() for /clear detection — removes all cache entries
  matching a key prefix (e.g., "trend_" to reset all sparkline history).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Cargo.lock

@@ -112,6 +112,7 @@ checksum = "c3e64b0cc0439b12df2fa678eae89a1c56a529fd067a9115f7827f1fffd22b32"
 name = "claude-statusline"
 version = "0.1.0"
 dependencies = [
+ "colorgrad",
  "criterion",
  "libc",
  "md-5",
@@ -123,6 +124,15 @@ dependencies = [
  "unicode-width",
 ]
 
+[[package]]
+name = "colorgrad"
+version = "0.7.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "faedab4fd8670120c2be7f49225fbdb8b6db6d46f04ce4f864b1f1cdd55e6400"
+dependencies = [
+ "csscolorparser",
+]
+
 [[package]]
 name = "criterion"
 version = "0.5.1"
@@ -200,6 +210,15 @@ dependencies = [
  "typenum",
 ]
 
+[[package]]
+name = "csscolorparser"
+version = "0.7.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5fda6aace1fbef3aa217b27f4c8d7d071ef2a70a5ca51050b1f17d40299d3f16"
+dependencies = [
+ "phf",
+]
+
 [[package]]
 name = "digest"
 version = "0.10.7"
@@ -322,6 +341,48 @@ version = "11.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d6790f58c7ff633d8771f42965289203411a5e5c68388703c06e14f24770b41e"
 
+[[package]]
+name = "phf"
+version = "0.11.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1fd6780a80ae0c52cc120a26a1a42c1ae51b247a253e4e06113d23d2c2edd078"
+dependencies = [
+ "phf_macros",
+ "phf_shared",
+]
+
+[[package]]
+name = "phf_generator"
+version = "0.11.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3c80231409c20246a13fddb31776fb942c38553c51e871f8cbd687a4cfb5843d"
+dependencies = [
+ "phf_shared",
+ "rand",
+]
+
+[[package]]
+name = "phf_macros"
+version = "0.11.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f84ac04429c13a7ff43785d75ad27569f2951ce0ffd30a3321230db2fc727216"
+dependencies = [
+ "phf_generator",
+ "phf_shared",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "phf_shared"
+version = "0.11.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "67eabc2ef2a60eb7faa00097bd1ffdb5bd28e62bf39990626a582201b7a754e5"
+dependencies = [
+ "siphasher",
+]
+
 [[package]]
 name = "plotters"
 version = "0.3.7"
@@ -368,6 +429,21 @@ dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "rand"
+version = "0.8.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "34af8d1a0e25924bc5b7c43c079c942339d8f0a8b57c39049bef581b46327404"
+dependencies = [
+ "rand_core",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.6.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ec0be4795e2f6a28069bec0b5ff3e2ac9bafc99e6a9a7dc3547996c5c816922c"
+
 [[package]]
 name = "rayon"
 version = "1.11.0"
@@ -496,6 +572,12 @@ dependencies = [
  "serde_core",
 ]
 
+[[package]]
+name = "siphasher"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b2aa850e253778c88a04c3d7323b043aeda9d3e30d5971937c1855769763678e"
+
 [[package]]
 name = "syn"
 version = "2.0.114"