feat: add proc-macro based `tmpl!` and display block template syntax

This introduces a workspace restructuring with separate library and
proc-macro crates, replacing the old declarative macros with a new proc
macro that supports simplified call syntax, implicit template variable
names, and mixed simple parameters with implementation blocks. Display
blocks (`??? >>> name` / `??? <<<`) provide conditionally included
sections with per-arm control, enabled by inserting a param key. The old
`macro_rules!` macros, deprecated module, and standalone test files are
removed in favor of comprehensive inline tests.

1 files changed, 34 insertions, 3 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b659aec..376b2b7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,12 +11,43 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
-- Simplified `tmpl!` macro syntax: supports `tmpl!(tmpl, block_name { key = val, ... })` form, removing the `+=` operator and parentheses around each parameter group
-- Old syntax `tmpl!(tmpl += { ... })` remains backward compatible
+- **Display blocks (`??? >>> name` / `??? <<<`)** — new template syntax for
+  conditionally included sections. Controlled by `params` key presence: default
+  hidden, enabled via `template.insert_param("name", "")`.
+- **Per-arm display block control** — each implementation arm can independently
+  enable display blocks by including the block name in its own parameter map,
+  e.g. `{ crate_name = "you", extra = "" }` enables `??? >>> extra` for that
+  arm only.
+- **`just_template_macros` proc-macro crate** — new `tmpl!` proc macro replaces
+  the old `macro_rules!` macros (`tmpl!`, `tmpl_param!`), supporting:
+  - `tmpl!(tmpl, key = val)` and `tmpl! { key = val }` call forms
+  - Mixed simple parameters and implementation blocks in one call
+  - Braced multi-parameter arms: `{ key = val, key = val }` inside impl blocks
+  - Implicit template variable name (defaults to `tmpl` when omitted)
+- **Comprehensive test suite** — `test_expand.rs` (direct API tests) and
+  `test_macros.rs` (macro syntax tests), covering all features.
+- `Template::add_impl` now uses `HashMap::entry(...).or_default()` for brevity.
+- Public documentation for `Template` fields.
 
 ### Changed
 
-- Documentation and test code unified to use the simplified `tmpl!` syntax
+- **Restructured to workspace layout** — root `Cargo.toml` is now a workspace
+  root. Library code moved to `just_template/`, proc-macro code to
+  `just_template_macros/`.
+- **Replaced `macro_rules!` macros with proc macro** — old `tmpl_param!` and
+  `tmpl!` (declarative) macros are removed in favor of the new `tmpl!` proc
+  macro from `just_template_macros`.
+- **`expand.rs` refactored** — added `apply_display_blocks()`, per-arm display
+  param merging, migrated from `mem::replace` to `std::mem::take`, and replaced
+  `.len() < 1` / `.len() > 0` with `.is_empty()` / `!is_empty()`.
+
+### Removed
+
+- Old deprecated module (`deprecated.rs`) containing the old `macro_rules!`
+  macros.
+- Standalone test files `test_input.txt` and `test_expect.txt` — replaced by
+  inline tests in `test_expand.rs`.
+- Root-level `src/lib.rs` and `src/test.rs` — moved into workspace crates.
 
 ## [0.1.3] - 2026-03-02