docs(readme): rewrite project overview and usage

README.md

@@ -1,28 +1,124 @@
 # iKv
 
-Standalone iKv C library.
+iKv is a small standalone C library for reading, writing, and building iKv data trees.
+It supports both text and binary formats, keeps the public API in a single header, and
+handles multiple on-disk versions behind one interface.
 
-Build:
-- CMake: `cmake -S . -B build && cmake --build build`
-- Scripted local build on Linux runners: `./demo/build.sh`
+## What it does
 
-Layout:
-- `include/ikv.h`: public API only.
-- `src/ikv.c`: shared implementation and loader dispatch.
-- `src/loaders/ikv1.c`: iKv1 loader.
-- `src/loaders/ikv2.c`: iKv2 loader.
-- `src/internal/ikv_internal.h`: private node layout and loader interface.
+- Parse iKv text from strings or files
+- Parse iKv binary blobs from memory or files
+- Build object and array trees in memory
+- Write text or binary output
+- Auto-detect `iKv1` vs `iKv2` for generic parse calls
+- Write the current format version by default, which is `iKv2`
 
-Behavior:
-- The generic parse APIs auto-detect iKv1 vs iKv2 and choose the correct loader.
-- The generic write APIs emit the current format version, which is `iKv2`.
-- Public callers do not depend on loader-specific headers or internal structs.
-- `iKv2` binary files now use an indexed root layout with a key table and payload offsets.
-- Parsing an `iKv2` binary file reads the root index first and loads individual top-level values on demand.
-- `iKv1` binary files still use the legacy full-tree format for compatibility.
+## Syntax preview
 
-Adding a new version:
-1. Add `src/loaders/ikv3.h` and `src/loaders/ikv3.c` exporting an `ikv_loader_t`.
-2. Implement that loader using the shared internal helpers or custom logic.
-3. Register the loader in `src/ikv.c`.
-4. Add the new version constant to `include/ikv.h` if it is part of the public API.
+```ikv
+ikv2 "player_save"
+{
+    "title" "iKv demo"
+    "version" 2
+    "player" {
+        "name" "jondoe"
+        "alive" true
+        "speed" 12.5
+    }
+    "inventory" [
+        "wrench"
+        "battery"
+        "map"
+    ]
+}
+```
+
+## Library example
+
+```c
+#include "ikv.h"
+
+ikv_node_t *root = ikv_create_object("demo");
+ikv_node_t *player = ikv_object_add_object(root, "player");
+
+ikv_object_set_string(root, "title", "iKv demo");
+ikv_object_set_int(root, "version", 2);
+ikv_object_set_string(player, "name", "jondoe");
+ikv_object_set_bool(player, "alive", true);
+
+ikv_write_file("demo_output.ikv", root);
+ikv_free(root);
+```
+
+## Build
+
+### CMake
+
+```sh
+cmake -S . -B build
+cmake --build build
+```
+
+This produces the reusable static library target:
+- `ikv`
+- `ikv::ikv` for CMake consumers
+
+Example consumer usage:
+
+```cmake
+add_subdirectory(path/to/iKv)
+target_link_libraries(your_target PRIVATE ikv::ikv)
+```
+
+### Script build
+
+For the repo-local non-CMake build path used in CI:
+
+```sh
+./demo/build.sh
+```
+
+## Project layout
+
+- `include/ikv.h`: public API
+- `src/ikv.c`: shared implementation and loader dispatch
+- `src/loaders/ikv1.c`: iKv1 loader
+- `src/loaders/ikv2.c`: iKv2 loader
+- `src/internal/ikv_internal.h`: private internals and loader interface
+- `demo/main.c`: small usage example
+- `demo/unit_test.c`: unit tests
+
+## Format behavior
+
+- Generic parse APIs auto-detect `iKv1` and `iKv2`
+- Generic write APIs default to `iKv2`
+- Public callers do not need loader-specific headers
+- `iKv2` binary files use an indexed root layout with key tables and payload offsets
+- `iKv1` binary files remain supported for compatibility
+
+## Public API
+
+The public interface is declared in [`include/ikv.h`](./include/ikv.h).
+Key areas include:
+
+- node creation and cleanup
+- object and array mutation
+- scalar accessors
+- text parse/write APIs
+- binary parse/write APIs
+- explicit versioned APIs when auto-detection is not desired
+
+## License
+
+This repository currently ships with the license text in [`LICENSE`](./LICENSE):
+
+- Creative Commons Attribution-ShareAlike 4.0 International (`CC BY-SA 4.0`)
+
+## Extending the format
+
+To add a new format version:
+
+1. Add `src/loaders/ikv3.h` and `src/loaders/ikv3.c` exporting an `ikv_loader_t`
+2. Implement the loader
+3. Register it in `src/ikv.c`
+4. Add a public version constant to `include/ikv.h` if needed