chore(merge): branch 'worktree-improvise-ewi-formula-crate'

Fixes: improvise-ewi

context/repo-map.md

@@ -1,8 +1,10 @@
 # Repository Map (LLM Reference)
 
 Terminal pivot-table modeling app. Rust, Ratatui TUI, command/effect architecture.
-Crate `improvise` v0.1.0-rc2, Apache-2.0, edition 2024.
+Cargo workspace, Apache-2.0, edition 2024. Root package `improvise` v0.1.0-rc2.
 Library + binary crate: `src/lib.rs` exports public modules, `src/main.rs` is the CLI entry.
+Sub-crates live under `crates/`:
+- `crates/improvise-formula/` — formula parser, AST (`Expr`, `BinOp`, `AggFunc`, `Formula`, `Filter`), `parse_formula`. Re-exported as `crate::formula` from the main crate via `pub use improvise_formula as formula;`.
 
 ---
 
@@ -153,7 +155,7 @@ pub enum CategoryKind { Regular, VirtualIndex, VirtualDim, VirtualMeasure, Label
 ### Formula System
 
 ```rust
-// src/formula/ast.rs
+// crates/improvise-formula/src/ast.rs
 pub enum Expr {
     Number(f64),
     Ref(String),                           // reference to an item name
@@ -172,7 +174,7 @@ pub struct Formula {
     pub filter: Option<Filter>,   // WHERE clause
 }
 
-// src/formula/parser.rs
+// crates/improvise-formula/src/parser.rs
 pub fn parse_formula(raw: &str, target_category: &str) -> Result<Formula>
 ```
 
@@ -383,11 +385,11 @@ Lines / tests / path — grouped by layer.
    6 /  0t  model/mod.rs
 ```
 
-### Formula layer
+### Formula layer (sub-crate `improvise-formula` under `crates/`)
 ```
- 461 / 29t  formula/parser.rs     Recursive descent parser → Formula AST
-  77 /  0t  formula/ast.rs        Expr, BinOp, AggFunc, Formula, Filter (data only)
-   5 /  0t  formula/mod.rs
+ 776 / 35t  crates/improvise-formula/src/parser.rs  Recursive descent parser → Formula AST
+  77 /  0t  crates/improvise-formula/src/ast.rs     Expr, BinOp, AggFunc, Formula, Filter (data only)
+   5 /  0t  crates/improvise-formula/src/lib.rs
 ```
 
 ### View layer