Add capability-scoped module API (Workstream D)

ModuleManifest gains a structured [[permissions]] field (bread-shared's
new ModulePermission/PermissionKind, shared between bread-cli and breadd
so the two never drift on what a permission "type" string means).

breadd now gives every third-party module's Lua chunk a scoped _ENV
instead of the shared global table: load_scoped_lua_file builds a fresh
`bread` table containing only baseline bindings (event subscription,
timers, json, module/store, logging, and the pure-Lua sugar built on top
of those) plus whatever the manifest's permissions grant, with a
metatable __index falling back to the real globals for everything else
(stdlib, require/package - so require("bread.devices") keeps working,
since builtins load unscoped and their closures capture that environment
lexically regardless of the caller's). _G is explicitly rebound to the
scoped table itself to close the obvious escape hatch. A module with no
manifest, or a manifest with no permissions key, keeps full ambient
access unchanged (today's behavior) but is now tracked as `ungated` in
module status and surfaced by `bread doctor`. An explicit `permissions =
[]` is scoped for real but not flagged, since that's a deliberate
declaration.

Adds `bread modules audit <name>`: a best-effort text scan of a module's
.lua files suggesting a [[permissions]] block to paste into its manifest.

Converts examples/modules/cpu-temp-widget.lua into a directory module
with a worked bread.module.toml (fs.read + widget) as the reference
example. Documentation.md gets a new "Capability-scoped modules" section
covering the taxonomy, the require()/closure mechanism, and an explicit
note that path/bin scoping is recorded but not yet enforced per-call -
that's the out-of-process module sandboxing workstream this manifest
schema is laid down for. API_VERSION bumped 1.4.0 -> 1.5.0.

examples/modules/cpu-temp-widget/bread.module.toml

@@ -0,0 +1,21 @@
+name = "cpu-temp-widget"
+version = "1.0.0"
+description = "Live CPU package temperature widget, read from hwmon sysfs"
+author = "bread"
+source = "local"
+installed_at = ""
+
+# This module only ever calls bread.fs.read (never .write) and
+# bread.widget.register/update — declaring exactly that is what makes
+# bread.exec, bread.bluetooth, bread.hyprland, bread.machine, bread.notify,
+# and bread.state all genuinely absent (nil) from its `bread` table at
+# runtime, rather than merely unused. `source`/`installed_at` above get
+# overwritten by `bread modules install`; they're placeholders for the
+# drop-in/copy-paste path.
+
+[[permissions]]
+type = "fs.read"
+path = "/sys/class/hwmon"
+
+[[permissions]]
+type = "widget"

examples/modules/cpu-temp-widget/init.lua

@@ -0,0 +1,73 @@
+-- cpu-temp-widget — live CPU package temperature, read straight from the
+-- k10temp hwmon sysfs node via bread.fs.read.
+--
+-- Demonstrates: WidgetPlacement "left_of_stats", a bread.every-polled
+-- widget reading real hardware state (the same category of readout
+-- breadbar's native CPU%/RAM stats already do in Rust — this shows it's
+-- just as easy from a drop-in Lua module), and the typed `style` vocabulary
+-- (color + weight) swapping based on a threshold so the widget visually
+-- flags when something's hot — no CSS, no guessing which class names the
+-- rendering app happens to define.
+--
+-- Drop-in: copy the whole cpu-temp-widget/ directory into
+-- ~/.config/bread/modules/ (or `bread modules install path/to/this/dir`).
+-- TEMP_PATH is specific to this machine (AMD, k10temp) — find yours with:
+--   grep -l k10temp /sys/class/hwmon/hwmon*/name
+-- and adjust below; a missing/unreadable path just shows "—" rather than
+-- erroring, since bread.fs.read returns nil (not an error) for that case.
+--
+-- This is also the worked example for the capability-manifest permission
+-- system (Documentation.md's "Capability-scoped modules" section): see the
+-- sibling bread.module.toml. It declares exactly the two permissions this
+-- module actually uses — `fs.read` (bread.fs.read, read-only) and `widget`
+-- (bread.widget.register/update) — nothing else. If you install it that
+-- way, bread.exec/bread.bluetooth/bread.hyprland/etc. are all genuinely
+-- absent (nil) from this module's `bread` table, not just unused.
+
+local M = bread.module({ name = "cpu-temp-widget", version = "1.0.0" })
+
+local TEMP_PATH = "/sys/class/hwmon/hwmon6/temp1_input"
+local HOT_THRESHOLD_C = 80
+
+local function read_temp_c()
+    local raw = bread.fs.read(TEMP_PATH)
+    if not raw then
+        return nil
+    end
+    return tonumber(raw) / 1000
+end
+
+local function widget_root(temp_c)
+    local text = temp_c and string.format("%.0f°C", temp_c) or "—"
+    local hot = temp_c ~= nil and temp_c >= HOT_THRESHOLD_C
+    return {
+        type = "box",
+        children = {
+            {
+                type = "label",
+                text = text,
+                style = hot and { color = "red", weight = "bold" } or { color = "dim" },
+            },
+            {
+                type = "progress",
+                value = temp_c and math.min(temp_c / 100, 1.0) or 0,
+                style = hot and { color = "red" } or nil,
+            },
+        },
+    }
+end
+
+function M.on_load()
+    bread.widget.register({
+        id = "cpu-temp",
+        placement = "left_of_stats",
+        tooltip = "CPU package temperature (Tctl)",
+        root = widget_root(read_temp_c()),
+    })
+
+    bread.every(5000, function()
+        bread.widget.update("cpu-temp", { root = widget_root(read_temp_c()) })
+    end)
+end
+
+return M