feat: P.0.lib.camera 2D camera state + begin/finish wrapper

.gitignore

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+build/
+*.log

README.md

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+# lib-core.camera
+
+P.0 2D camera state + begin/finish wrapper. Holds `target = {x, y}` + `zoom`,
+wraps `engine.render.camera_2d_begin/end` with current state.
+
+- Lib-ID: `lib-core.camera`
+- Version: `0.1.0`
+- Spec: `meta/docs/superpowers/specs/2026-05-09-p0-lib-camera-design.md`
+
+Forward-compat stubs (DEPRECATED-MVP) for follow, set_bounds, lerp_to, shake,
+set_rotation. See `meta/docs/architecture/render-pipeline.md` and
+`meta/docs/architecture/map-topology.md §7.3` for full target context.
+
+## API
+- `camera.set_target(x, y)` — set world-coords for screen-center
+- `camera.set_zoom(z)` — set zoom (positive number)
+- `camera.target() → {x, y}` — current target
+- `camera.zoom() → number` — current zoom
+- `camera.begin()` — push camera transform (must be inside render hook)
+- `camera.finish()` — pop camera transform (`end` is Lua keyword)
+
+## Consumer pattern
+```lua
+local camera = require("lib-core.camera")
+camera.set_target(256, 256)  -- world-coords
+camera.set_zoom(1.0)
+function render(ctx)
+    engine.render.clear_color(...)
+    camera.begin()
+    -- draw world here
+    camera.finish()
+end
+```

init.lua

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+-- =====================================================================
+-- lib-core.camera — 2D Camera State (P.0)
+-- See: meta/docs/superpowers/specs/2026-05-09-p0-lib-camera-design.md
+--
+-- Scope: target + zoom state + begin/finish wrapper.
+-- Forward-compat stubs (DEPRECATED-MVP):
+--   - follow(entity)            -- lib-core.actor slice
+--   - set_bounds(map_id)         -- when map-bounds matter
+--   - lerp_to(target, dt)        -- smooth-follow / animation slice
+--   - shake(intensity, dur)      -- effects/juice slice
+--   - set_rotation(deg)          -- closed-topology slice
+-- =====================================================================
+
+local target_x = 0
+local target_y = 0
+local zoom_v   = 1.0
+
+local M = {}
+
+function M.set_target(x, y)
+    if type(x) ~= "number" or type(y) ~= "number" then
+        error("camera.set_target: x and y must be numbers")
+    end
+    target_x = x
+    target_y = y
+end
+
+function M.set_zoom(z)
+    if type(z) ~= "number" or z <= 0 then
+        error(string.format("camera.set_zoom: zoom must be a positive number, got %s",
+            tostring(z)))
+    end
+    zoom_v = z
+end
+
+function M.target()
+    return { x = target_x, y = target_y }
+end
+
+function M.zoom()
+    return zoom_v
+end
+
+function M.begin()
+    engine.render.camera_2d_begin(target_x, target_y, zoom_v)
+end
+
+function M.finish()
+    engine.render.camera_2d_end()
+end
+
+-- DEPRECATED-MVP: forward-compat stubs for later slices
+-- function M.follow(entity)            -- lib-core.actor slice
+-- function M.set_bounds(map_id)        -- bounds-clamping slice
+-- function M.lerp_to(target, dt)       -- smooth-follow slice
+-- function M.shake(intensity, dur)     -- effects/juice slice
+-- function M.set_rotation(deg)         -- closed-topology slice
+
+return M

manifest.lib

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+{"id":"lib-core.camera","version":"0.1.0","api_min":"0.1"}