docs(demos): rebrand Acme Corp -> QuantumNexum in asciinema casts

Replace placeholder "Acme Corp" / "AcmeCorp" organization name with
"QuantumNexum" across the three demo casts that referenced it:

- the-intern.cast:   Signer O= field (sign + verify output)
- quantum-panic.cast: Signer O= field (ML-DSA sign output)
- the-heist.cast:    hex-editor dump (ASCII + matching hex bytes)

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

Author: rayketcham

docs/demos/quantum-panic.cast

@@ -101,7 +101,7 @@
 [11.5, "o", "\r\n"]
 [11.7, "o", "\u001b[1;32m✔ Signed successfully (post-quantum)\u001b[0m\r\n"]
 [11.9, "o", "  Output    : app.pqc.exe\r\n"]
-[12.1, "o", "  Signer    : CN=Corp PQC Signing CA, O=Acme Corp\r\n"]
+[12.1, "o", "  Signer    : CN=Corp PQC Signing CA, O=QuantumNexum\r\n"]
 [12.3, "o", "  \u001b[1;32mAlgorithm  : ML-DSA-65 (NIST FIPS 204) — quantum-resistant\u001b[0m\r\n"]
 [12.5, "o", "  Hash      : SHA-512\r\n"]
 [12.7, "o", "  Sig size  : 3309 bytes\r\n"]

docs/demos/the-heist.cast

@@ -23,7 +23,7 @@
 [3.29, "o", "e"]
 [3.36, "o", "\r\n"]
 [3.6, "o", "  Opening signed.exe in hex editor...\r\n"]
-[3.8, "o", "  Offset 0x00004800: \u001b[2m41 63 6D 65 43 6F 72 70\u001b[0m  AcmeCorp\r\n"]
+[3.8, "o", "  Offset 0x00004800: \u001b[2m51 75 61 6E 74 75 6D 4E\u001b[0m  QuantumN\r\n"]
 [4.0, "o", "  \u001b[1;31mPatching offset 0x00004800...\u001b[0m\r\n"]
 [4.2, "o", "  \u001b[1;31mWriting: 43 68 61 64 57 61 73 48\u001b[0m  ChadWasH\r\n"]
 [4.4, "o", "  \u001b[1;31mWriting: 65 72 65 00 00 00 00 00\u001b[0m  ere.....\r\n"]

docs/demos/the-intern.cast

@@ -117,7 +117,7 @@
 [15.85, "o", "\r\n"]
 [16.0, "o", "\u001b[1;32m✔ Signed successfully\u001b[0m\r\n"]
 [16.2, "o", "  Output : signed.exe\r\n"]
-[16.4, "o", "  Signer : CN=Corp Desktop CA, O=Acme Corp\r\n"]
+[16.4, "o", "  Signer : CN=Corp Desktop CA, O=QuantumNexum\r\n"]
 [16.6, "o", "  Algo   : SHA256withRSA\r\n"]
 [16.8, "o", "  TSA    : tsa.corp.internal (2026-03-25T09:04:33Z)\r\n"]
 [17.0, "o", "  Elapsed: 312ms\r\n"]
@@ -154,7 +154,7 @@
 [20.1, "o", "  \u001b[1;32m✔\u001b[0m Authenticode hash: MATCH\r\n"]
 [20.3, "o", "  \u001b[1;32m✔\u001b[0m Certificate chain: VALID (3 certs)\r\n"]
 [20.5, "o", "  \u001b[1;32m✔\u001b[0m Timestamp: VALID — 2026-03-25T09:04:33Z\r\n"]
-[20.7, "o", "  \u001b[1;32m✔\u001b[0m Signer: CN=Corp Desktop CA, O=Acme Corp\r\n"]
+[20.7, "o", "  \u001b[1;32m✔\u001b[0m Signer: CN=Corp Desktop CA, O=QuantumNexum\r\n"]
 [20.9, "o", "  \u001b[1;32m✔\u001b[0m Algorithm: SHA256withRSA (2048-bit)\r\n"]
 [21.1, "o", "\r\n"]
 [21.5, "o", "\u001b[1;32m❯\u001b[0m "]