chore: condense core and domain README API sections

Replace verbose impl blocks and function signatures with concise
narrative descriptions. Remove implementation details (bounded sizes,
dispatch strategy, internal lifecycle functions) from developer-facing
docs while preserving the types and traits consumers need.

Author: fulsomenko

crates/kanban-core/README.md

@@ -110,81 +110,15 @@ pub trait Service<T, Id>: Send + Sync {
 
 ### Graph
 
-`Graph<E>` — Generic directed graph data structure used for card dependencies:
+Generic directed graph (`Graph<E>`) for modeling relationships between entities. Used by `kanban-domain` for card dependencies. Edge types implement the `Edge` trait, which declares whether cycles are allowed — the graph enforces DAG constraints automatically for acyclic edge types.
 
-```rust
-pub struct Graph<E: Edge> {
-    // ...
-}
-
-pub trait Edge: Clone + PartialEq {
-    fn is_acyclic(&self) -> bool;
-}
-
-pub trait GraphNode {
-    fn node_id(&self) -> Uuid;
-}
-```
-
-- Add/remove edges between nodes
-- Automatic cycle detection for acyclic edge types
-- Query neighbors, parents, and children by edge type
-- Edge direction filtering (`Outgoing`, `Incoming`, `Both`)
-
-### InputState
-
-Cursor-aware text input buffer with correct multi-byte UTF-8 handling:
-
-```rust
-pub struct InputState { /* private fields */ }
-
-impl InputState {
-    pub fn new() -> Self
-    pub fn insert_char(&mut self, c: char)
-    pub fn backspace(&mut self)
-    pub fn move_left(&mut self)
-    pub fn move_right(&mut self)
-    pub fn value(&self) -> &str
-    pub fn cursor_byte_offset(&self) -> usize
-}
-```
-
-### SelectionState
-
-Generic single-item selection for list navigation:
-
-```rust
-pub struct SelectionState { /* private fields */ }
-
-impl SelectionState {
-    pub fn new() -> Self
-    pub fn select(&mut self, index: usize)
-    pub fn selected(&self) -> Option<usize>
-    pub fn next(&mut self, total: usize)
-    pub fn prev(&mut self)
-    pub fn jump_to_first(&mut self)
-    pub fn jump_to_last(&mut self, total: usize)
-    pub fn clamp(&mut self, total: usize)
-}
-```
+### State Primitives
 
-### Pagination
+UI-agnostic building blocks used by the TUI and available to any consumer:
 
-Viewport pagination with scroll position management:
-
-```rust
-pub struct PageInfo {
-    pub visible_indices: Vec<usize>,
-    pub items_above: usize,
-    pub items_below: usize,
-}
-
-impl Page {
-    pub fn new(viewport_height: usize) -> Self
-    pub fn calculate(&self, total_items: usize, selected: usize) -> PageInfo
-    pub fn scroll_to_visible(&mut self, index: usize)
-}
-```
+- **`InputState`** — Text input buffer with cursor tracking and multi-byte UTF-8 support
+- **`SelectionState`** — Single-item selection for navigable lists (next/prev, jump to first/last, clamp to bounds)
+- **`Page` / `PageInfo`** — Viewport pagination that calculates visible items, scroll offset, and above/below counts
 
 ## Architecture
 

crates/kanban-domain/README.md

@@ -156,30 +156,14 @@ pub trait DependencyGraph {
 - Edges referencing a deleted or archived card are automatically cleaned up
 - Integrated into board persistence (import/export)
 
-### Card Lifecycle
-
-Pure domain functions for card state transitions:
-
-```rust
-pub fn compute_completion_toggle(card: &Card, board: &Board) -> ToggleResult;
-pub fn compute_move_to_column(card: &Card, target_column_id: ColumnId, board: &Board) -> MoveResult;
-pub fn compute_auto_completion_on_create(column_id: ColumnId, board: &Board) -> CardStatus;
-pub fn compact_positions(cards: &mut [Card]);
-pub fn next_position_in_column(cards: &[Card], column_id: ColumnId) -> u32;
-```
-
 ### Sorting & Filtering
 
-**SortBy** — Enum dispatch for card sorting (no dyn dispatch):
+**SortBy** — Enum dispatch for card sorting:
 
 ```rust
 pub enum SortBy {
     Points, Priority, CreatedAt, UpdatedAt, Status, Position, CardNumber
 }
-
-impl SortBy {
-    pub fn sort_by(&self, cards: &mut [Card]);
-}
 ```
 
 **CardFilter** trait + concrete filters:
@@ -208,40 +192,20 @@ let cards = CardQueryBuilder::new(&all_cards)
 ### History & Snapshots
 
 ```rust
-pub struct HistoryManager { /* bounded undo/redo stacks, max 100 entries */ }
+pub struct HistoryManager { /* undo/redo stacks */ }
 pub struct Snapshot { /* point-in-time state of all kanban data */ }
-
-impl HistoryManager {
-    pub fn push_undo(&mut self, snapshot: Snapshot);
-    pub fn undo(&mut self) -> Option<Snapshot>;
-    pub fn redo(&mut self) -> Option<Snapshot>;
-    pub fn can_undo(&self) -> bool;
-    pub fn can_redo(&self) -> bool;
-}
-
-impl Snapshot {
-    pub fn to_json_bytes(&self) -> KanbanResult<Vec<u8>>;
-    pub fn from_json_bytes(bytes: &[u8]) -> KanbanResult<Self>;
-}
 ```
 
+`HistoryManager` maintains undo and redo stacks of `Snapshot` values. Each snapshot captures the full board state and can be serialized to/from JSON bytes.
+
 ### Export / Import
 
 ```rust
 pub struct BoardExporter;
 pub struct BoardImporter;
-
-impl BoardExporter {
-    pub fn export_board(board: &Board, ...) -> BoardExport;
-    pub fn export_all_boards(...) -> AllBoardsExport;
-}
-
-impl BoardImporter {
-    pub fn import(data: &str) -> KanbanResult<ImportedEntities>;
-}
 ```
 
-Supports V1 and V2 format detection with automatic migration.
+`BoardExporter` produces single-board or all-boards JSON exports. `BoardImporter` reads JSON with automatic V1/V2 format detection and migration.
 
 ## Architecture