Feat v0.8.0 files module (#67)

Co-authored-by: Jeffrey Smith <jasafpro@gmail.com>
Co-committed-by: Jeffrey Smith <jasafpro@gmail.com>

CHANGELOG.md

@@ -2,6 +2,30 @@
 
 All notable changes to Armature are documented here.
 
+## v0.8.0 — Files Module
+
+New `files` sandbox module. Bridges the existing ObjectStore (PVC/S3) into
+the Starlark sandbox with extension-scoped key namespacing.
+
+**files module (permissions: `files.read`, `files.write`)**
+
+- `files.put(name, content, content_type, metadata)` — store a file with optional metadata companion. Accepts string or bytes content. 50 MB default limit (configurable via `EXT_FILES_MAX_SIZE`).
+- `files.get(name)` — read a file. Returns dict with `content` (bytes), `content_type`, `size`, `metadata`. Returns None if not found.
+- `files.meta(name)` — read metadata only (no content transfer).
+- `files.list(prefix, limit)` — list files by prefix. Returns list of dicts. Filters out internal `_meta/` companions.
+- `files.delete(name)` — delete a file and its metadata companion. Idempotent.
+- `files.delete_prefix(prefix)` — delete all files under a prefix.
+- `files.exists(name)` — check existence without reading.
+
+**Internal**
+
+- New file: `sandbox/files_module.go`.
+- New permission constants: `ExtPermFilesRead`, `ExtPermFilesWrite`.
+- `ObjectStore` interface gains `List(ctx, prefix, limit)` method; implemented for PVC and S3.
+- Runner wiring: `SetObjectStore()` setter, `buildModulesWithLibCtx` creates files module when permission granted.
+- All keys scoped to `ext/{packageID}/`. Metadata stored as companion JSON at `ext/{packageID}/_meta/{name}`.
+- 16 new tests (15 files module + 1 PVC list).
+
 ## v0.7.12 — Concurrent Execution Primitive
 
 New `batch` sandbox module. Enables extensions to parallelize arbitrary