docs: migrate README to API-Doc-Convention (S2-cascade.libs)

Restructured per ADR-0038: Abstract + bold-list Badges + Topology H2
+ H3-API-Subsections (one per public function) + Conventions/Consumer
pattern/CHANGELOG/References.

Topology auto-populated via Sporel.exe --lint --fix. Pre-commit hook
installed via --install-hooks.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

README.md

@@ -1,50 +1,80 @@
 # lib-core.interaction
 
-P.0 proximity-trigger + action-dispatch lib. Register triggers with
-`(target_x, target_y, range, action_name, callback)`; per-frame
-`update(actor_x, actor_y)` checks distance + `was_action_pressed` and
-fires the nearest matching trigger per `action_name`.
+Proximity-trigger + action-dispatch. Register triggers with `(target_x, target_y, range, action_name, callback)`; per-frame `update(actor_x, actor_y)` checks distance + `was_action_pressed` and fires the nearest matching trigger per `action_name`.
 
-- Lib-ID: `lib-core.interaction`
-- Version: `0.1.0`
-- Spec: `meta/docs/superpowers/specs/2026-05-10-p0-lib-interaction-design.md`
+**Version:** 0.1.0  
+**Lib-ID:** lib-core.interaction  
+**Requires:** lib-core.input v>=0.4.0  
+**Tags:** interaction, trigger, proximity, dispatch
 
-Forward-compat stubs (DEPRECATED-MVP) for AABB-targets, action-effect-
-pipeline integration, visual-feedback / moodlet, action-cycling,
-hold-vs-press, per-action-resolution-override, callback pcall-wrap,
-target-entity-binding, range-shape variants.
+## Topology
+
+<!-- topology:start (auto-generated; do not edit) -->
+```mermaid
+graph LR
+  this["lib-core.interaction"]
+  lib_core_input["lib-core.input"]
+  this --> lib_core_input
+```
+<!-- topology:end -->
 
 ## API
-- `interaction.register(target_x, target_y, range, action_name, callback) → id`
-- `interaction.unregister(id)` — silent no-op if id unknown
-- `interaction.update(actor_x, actor_y)` — proximity-check + dispatch
-- `interaction.list() → array of { id, target_x, target_y, range, action_name }`
-- `interaction.trigger_count() → integer`
+
+### `interaction.register(target_x, target_y, range, action_name, callback)`
+**Syntax:** `interaction.register(target_x: number, target_y: number, range: number, action_name: string, callback: fun(info: table)) -> id`
+
+**Example:**
+```lua
+local id = interaction.register(144, 144, 40, "interact", function(info)
+    engine.print("you pressed interact at distance " .. info.distance)
+end)
+```
+
+**Description:** Registers a proximity-trigger. Range is scalar pixel-radius. When the action's press-edge fires inside range, the callback is called with `info = { actor_x, actor_y, target_x, target_y, distance, trigger_id, action_name }`. Returns an opaque id used for `unregister`. Loud `error(...)` on misuse (non-number coords, non-positive range, non-string action, non-function callback).
+
+### `interaction.unregister(id)`
+**Syntax:** `interaction.unregister(id: id) -> void`
+
+**Description:** Removes a trigger. Silent no-op if `id` is unknown.
+
+### `interaction.update(actor_x, actor_y)`
+**Syntax:** `interaction.update(actor_x: number, actor_y: number) -> void`
+
+**Example:**
+```lua
+function update(ctx, dt)
+    interaction.update(player_center_x, player_center_y)
+end
+```
+
+**Description:** Per-frame proximity-check + dispatch. Per `action_name`, only the NEAREST in-range trigger fires that frame; different `action_name`s are independent (all may fire same frame).
+
+### `interaction.list()`
+**Syntax:** `interaction.list() -> {id: id, target_x: number, target_y: number, range: number, action_name: string}[]`
+
+**Description:** Returns an array of trigger-records. Debug + UI inspection.
+
+### `interaction.trigger_count()`
+**Syntax:** `interaction.trigger_count() -> integer`
+
+**Description:** Returns the number of currently registered triggers.
 
 ## Conventions
-- Targets are points (not AABBs in P.0). `range` is scalar pixel-radius.
-- Distance: `engine.spatial.distance(actor, target) ≤ range`.
-- Multi-match resolution: per `action_name`, only NEAREST in-range trigger
-  fires per update. Different `action_name`s are independent (all may fire
-  the same frame).
+
+- Targets are points (not AABBs in v0.1.0). `range` is scalar pixel-radius.
+- Distance: `engine.spatial.distance(actor, target) <= range`.
+- Multi-match resolution: per `action_name`, only NEAREST in-range trigger fires per update.
 - Was-pressed semantics: `input.was_action_pressed` (single-frame edge).
-- Callback receives `info = { actor_x, actor_y, target_x, target_y,
-  distance, trigger_id, action_name }`. Closures may ignore the arg
-  (`function() ... end` is legal).
-- Loud Lua-errors on API misuse (non-number coords, non-positive range,
-  non-string action_name, non-function callback).
-- Silent-accept for `action_name` that hasn't been registered with
-  `lib-core.input` — the trigger simply never fires (matches input-lib's
-  silent-false convention).
-- Callback errors bubble up (no pcall-wrap in P.0). Resilience is
-  E.9 refactor target.
+- Silent-accept for `action_name` that hasn't been bound with `lib-core.input` — trigger simply never fires.
+- Callback errors bubble up (no pcall-wrap in v0.1.0).
 
 ## Consumer pattern
+
 ```lua
 local interaction = require("lib-core.interaction")
 local input       = require("lib-core.input")
 
-input.bind("interact", { engine.input.KEY_E })
+input.bind("interact", { "e" })
 
 local sign = { x = 144, y = 144, text = "Hier steht: ..." }
 interaction.register(sign.x, sign.y, 40, "interact", function(info)
@@ -52,7 +82,18 @@ interaction.register(sign.x, sign.y, 40, "interact", function(info)
 end)
 
 function update(ctx, dt)
-    -- (after player.update; reads player center)
     interaction.update(player_center_x, player_center_y)
 end
 ```
+
+## CHANGELOG
+
+### v0.1.0 (P.0)
+- Initial release: register/unregister + per-frame proximity + nearest-per-action dispatch.
+
+## References
+
+- Spec v0.1.0 (P.0): `meta/docs/superpowers/specs/2026-05-10-p0-lib-interaction-design.md`
+- ADR-0001 (engine knows verbs, libs bring nouns)
+- ADR-0031 (pixel-convention: Y-down-positive)
+- ADR-0038 (API-Doc-Convention)