rename: IAMROOT → SKELETONKEY across the entire project

Breaking change. Tool name, binary name, function/type names,
constant names, env vars, header guards, file paths, and GitHub
repo URL all rebrand IAMROOT → SKELETONKEY.

Changes:
  - All "IAMROOT" → "SKELETONKEY" (constants, env vars, enum
    values, docs, comments)
  - All "iamroot" → "skeletonkey" (functions, types, paths, CLI)
  - iamroot.c → skeletonkey.c
  - modules/*/iamroot_modules.{c,h} → modules/*/skeletonkey_modules.{c,h}
  - tools/iamroot-fleet-scan.sh → tools/skeletonkey-fleet-scan.sh
  - Binary "iamroot" → "skeletonkey"
  - GitHub URL KaraZajac/IAMROOT → KaraZajac/SKELETONKEY
  - .gitignore now expects build output named "skeletonkey"
  - /tmp/iamroot-* tmpfiles → /tmp/skeletonkey-*
  - Env vars IAMROOT_MODPROBE_PATH etc. → SKELETONKEY_*

New ASCII skeleton-key banner (horizontal key icon + ANSI Shadow
SKELETONKEY block letters) replaces the IAMROOT banner in
skeletonkey.c and README.md.

VERSION: 0.3.1 → 0.4.0 (breaking).

Build clean on Debian 6.12.86. `skeletonkey --version` → 0.4.0.
All 24 modules still register; no functional code changes — pure
rename + banner refresh.

docs/ARCHITECTURE.md

@@ -14,7 +14,7 @@ modules/<module_name>/
 ├── MODULE.md                  # Human-readable writeup of the bug
 ├── NOTICE.md                  # Credits to original researcher
 ├── kernel-range.json          # Machine-readable affected kernels
-├── module.c                   # Implements iamroot_module interface
+├── module.c                   # Implements skeletonkey_module interface
 ├── module.h
 ├── detect/
 │   ├── auditd.rules           # blue team detection
@@ -24,10 +24,10 @@ modules/<module_name>/
 └── tests/                     # per-module tests (run in CI matrix)
 ```
 
-### `iamroot_module` interface (planned, Phase 1)
+### `skeletonkey_module` interface (planned, Phase 1)
 
 ```c
-struct iamroot_module {
+struct skeletonkey_module {
     const char *name;           /* "copy_fail" */
     const char *cve;            /* "CVE-2026-31431" */
     const char *summary;        /* one-line description */
@@ -35,29 +35,29 @@ struct iamroot_module {
     /* Return 1 if host appears vulnerable, 0 if patched/immune,
      * -1 if probe couldn't run. May call entrybleed_leak_kbase()
      * etc. from core/ if a leak primitive is needed. */
-    int (*detect)(struct iamroot_host *host);
+    int (*detect)(struct skeletonkey_host *host);
 
     /* Run the exploit. Caller has already passed the
      * authorization gate. Returns 0 on root acquired,
      * nonzero on failure. */
-    int (*exploit)(struct iamroot_host *host, struct iamroot_opts *opts);
+    int (*exploit)(struct skeletonkey_host *host, struct skeletonkey_opts *opts);
 
     /* Apply a runtime mitigation for this CVE (sysctl, module
      * blacklist, etc.). Returns 0 on success. NULL if no
      * mitigation is offered. */
-    int (*mitigate)(struct iamroot_host *host);
+    int (*mitigate)(struct skeletonkey_host *host);
 
     /* Undo --exploit-backdoor or --mitigate side effects. */
-    int (*cleanup)(struct iamroot_host *host);
+    int (*cleanup)(struct skeletonkey_host *host);
 
     /* Affected kernel version range, distros covered, etc. */
-    const struct iamroot_kernel_range *ranges;
+    const struct skeletonkey_kernel_range *ranges;
     size_t n_ranges;
 };
 ```
 
 Modules register themselves at link time via a constructor-attribute
-table. The top-level `iamroot` binary iterates the registry on each
+table. The top-level `skeletonkey` binary iterates the registry on each
 invocation.
 
 ## Shared `core/`
@@ -78,7 +78,7 @@ Code that more than one module needs lives in `core/`:
 
 ## Top-level dispatcher
 
-`iamroot.c` (planned, Phase 1) is the CLI entry point. Responsibilities:
+`skeletonkey.c` (planned, Phase 1) is the CLI entry point. Responsibilities:
 
 1. Parse args (`--scan`, `--exploit <name>`, `--mitigate`,
    `--detect-rules`, `--cleanup`, etc.)
@@ -109,7 +109,7 @@ the module).
 1. `git checkout -b add-cve-XXXX-NNNN`
 2. `cp -r modules/_stubs/_template modules/<module_name>`
 3. Fill in `MODULE.md`, `NOTICE.md`, `kernel-range.json`
-4. Implement `module.c` exposing the `iamroot_module` interface
+4. Implement `module.c` exposing the `skeletonkey_module` interface
 5. Ship at least one detection rule under `detect/`
 6. Add tests under `tests/`
 7. PR. CI runs the matrix. If it lands root on at least one