feat(minga): minga-vfs — proyecta el repo como filesystem FUSE

minga-vfs deja de ser un stub: monta el repositorio direccionado por
contenido como un filesystem FUSE de sólo lectura. roots/<hash> da el
código fuente reconstruido (formato normalizado) de cada raíz del MST;
cas/<hash> resuelve cualquier hash bajo demanda como S-expression.

Capas separadas: render (SemanticNode→texto, puro) + source (contrato
NodeSource, backends sled/memoria) + fs (único módulo con fuser).
Nuevo subcomando `minga mount <punto>`. Dep fuser 0.15 sin libfuse-dev
(default-features = false). 14 tests nuevos, sin regresión en minga-cli.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Cargo.lock

@@ -4690,6 +4690,21 @@ version = "2.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e6d5a32815ae3f33302d95fdcb2ce17862f8c65363dcfd29360480ba1001fc9c"
 
+[[package]]
+name = "fuser"
+version = "0.15.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "53274f494609e77794b627b1a3cddfe45d675a6b2e9ba9c0fdc8d8eee2184369"
+dependencies = [
+ "libc",
+ "log",
+ "memchr",
+ "nix 0.29.0",
+ "page_size",
+ "smallvec",
+ "zerocopy",
+]
+
 [[package]]
 name = "futf"
 version = "0.1.5"
@@ -7676,6 +7691,7 @@ dependencies = [
  "minga-core",
  "minga-p2p",
  "minga-store",
+ "minga-vfs",
  "notify",
  "rpassword",
  "tempfile",
@@ -7753,7 +7769,11 @@ dependencies = [
 name = "minga-vfs"
 version = "0.1.0"
 dependencies = [
+ "fuser",
+ "libc",
  "minga-core",
+ "minga-store",
+ "tempfile",
 ]
 
 [[package]]
@@ -9501,6 +9521,16 @@ dependencies = [
  "sha2",
 ]
 
+[[package]]
+name = "page_size"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "30d5b2194ed13191c1999ae0704b7839fb18384fa22e49b57eeaa97d79ce40da"
+dependencies = [
+ "libc",
+ "winapi",
+]
+
 [[package]]
 name = "pageant"
 version = "0.1.0"