feat(inspector): port the terminal inspector

Ports ZIG/src/inspector (the Dear ImGui terminal inspector) as the
ghostty-inspector crate using dear-imgui-rs + dear-imgui-glow (imgui-rs
lacks a safe docking API): screen, modes, keyboard events, terminal IO
/ VT sequence log with filtering, cell inspector with picking, page
list, renderer and size/font info, with Ghostty's docking layout. The
crate denies unsafe except a single dock.rs module wrapping DockBuilder.

GTK: imgui_widget, inspector_widget and inspector_window classes with
their blueprints replace the former no-op; ctrl+shift+i toggles the
inspector window.

Core: activate/deactivate hooks, key event and mouse recording, and VT
stream recording in termio while an inspector is active, as in Zig;
overlay features reach the renderer through an InspectorHook on the
render state. The debug input replay hook gained inspector-screenshot/
click/scroll steps used to verify all tabs in the real app.

Deviations: font size scales with the display scale instead of Zig's
fixed 16*2; pop-out dock splits apply one frame later; DCS/APC
descriptions are approximated.

Test Plan:
- cargo test -p ghostty-inspector (15 incl. headless full-UI draw)
- cargo test -p ghostty-core --test e2e_inspector (4)

crates/ghostty-inspector/Cargo.toml

@@ -0,0 +1,46 @@
+[package]
+name = "ghostty-inspector"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+[dependencies]
+dear-imgui-rs = "0.19"
+ghostty-font.workspace = true
+ghostty-input.workspace = true
+ghostty-renderer.workspace = true
+ghostty-terminal.workspace = true
+ghostty-vt.workspace = true
+log = "0.4"
+
+[lints.rust]
+unsafe_code = "deny"
+
+[lints.clippy]
+pedantic = { level = "warn", priority = -1 }
+todo = "warn"
+unwrap_used = "warn"
+# Porting a low-level terminal emulator involves a lot of intentional
+# numeric casts and long state-machine functions; these pedantic lints are
+# noise for this codebase.
+cast_possible_truncation = "allow"
+cast_possible_wrap = "allow"
+cast_sign_loss = "allow"
+cast_precision_loss = "allow"
+cast_lossless = "allow"
+module_name_repetitions = "allow"
+too_many_lines = "allow"
+missing_errors_doc = "allow"
+missing_panics_doc = "allow"
+similar_names = "allow"
+struct_excessive_bools = "allow"
+fn_params_excessive_bools = "allow"
+match_same_arms = "allow"
+unreadable_literal = "allow"
+many_single_char_names = "allow"
+doc_markdown = "allow"
+must_use_candidate = "allow"
+return_self_not_must_use = "allow"
+used_underscore_binding = "allow"
+large_stack_arrays = "allow"
+inline_always = "allow"