feat(e10): SIC e10 part marker client, pattern generator and eDNC simulator

Groundwork for replacing a Telesis pinstamp with a SIC Marking e10 while
keeping the existing eDNC/MarkTelesis operator workflow. MarkTelesis has a
hardcoded marker-type enum and eDNC is serial-only, so the plan is a
translator that impersonates a Telesis controller on a COM port. These are
the pieces that translator will be built from, all verified against a real
e10 (a P63, firmware "E10 P63 (20140924)").

scripts/e10-client.py
  e10-V6 protocol client. Marking path and file transfer both use the BINARY
  protocol: the text protocol uses space as its delimiter, so it cannot carry
  a field cleared to a single space nor the space runs in real marked text,
  and it has no checksum. Includes fault decoding against the manual's fig 1,
  and a guard that refuses to overflow a variable's declared buffer.

scripts/make-e10-pattern.py
  Builds marking files with DECLARED variables. The controller's own protocol
  cannot create one: NEWFILE/INSERTTEXTLINE/SAVEFILE writes the reference but
  leaves the variable count at zero, and SETVAR then fails. Template-based,
  copying through byte-for-byte everything the format notes do not explain.

scripts/simulate-ednc.py
  Parses a part program, substitutes tokens and emits the byte-exact frames
  MarkTelesis would send, then translates them for the e10 and can drive one.
  The wire format came from disassembling MarkTelesis.exe rather than from a
  capture: frame builder at 0x401cf0, and the type letters at their call
  sites. Note there is no station ID, unlike the Backup470 dialect.

scripts/fake-telesis.py
  Answers as a Telesis controller so MarkTelesis will hold a conversation
  long enough to be recorded, with switches to force NAK and timeout paths.

reference/e10/
  52-file snapshot off the bench controller, used as the corpus for reversing
  the MARK_V5.0 format and for testing without hardware. ConfigCtrl is
  excluded and gitignored - it stores the supervisor password in cleartext.
  GE part programs are excluded for the same reason.

Three hardware findings worth knowing:
  - The controller TRUNCATES SILENTLY to a variable's declared buffer size
    while SETVAR still answers ok, and GETVAR echoes the full value back so
    it cannot detect this. Guarded client-side against the size in the file.
  - It refuses to mark when a referenced variable is unset, which makes an
    unset field fail loudly rather than marking the previous part's data.
  - Setting variables does not modify the stored file, so backups will not
    churn on every marked part.

reference/e10/README.md

@@ -0,0 +1,31 @@
+# SIC e10 reference snapshot
+
+Pulled off the bench controller (a P63, firmware `E10 P63 (20140924)`) on
+2026-08-27 with `scripts/e10-client.py backup`. 52 files: marking files,
+scribble logos, and the controller's own config files.
+
+Used as the reference corpus for reversing the `MARK_V5.0` marking file format
+and for testing the e10 client without hardware attached.
+
+## Deliberately missing: ConfigCtrl
+
+`ConfigCtrl` is the controller configuration file. **It stores the programmer
+and supervisor password in cleartext**, so it is not in this repo and must
+never be committed. It is kept outside git at
+`~/pxe-images/e10-ConfigCtrl-2026-08-27.kind1`, mode 0600, following the same
+convention as the other site-sensitive artefacts (ADR-015).
+
+`.gitignore` blocks `ConfigCtrl*` and `*.kind1` under this directory so a
+future snapshot cannot reintroduce it by accident.
+
+This has a direct consequence for the backup design: **any e10 snapshot that
+includes the controller config contains a live credential.** Whatever ACL
+protects the partmarker backup tree on the share has to account for that, and
+the ShopDB asset panel must never render the file's contents.
+
+## Part programs
+
+GE part programs are NOT in this repo - they carry part numbers and marking
+content. They live outside git at `~/pxe-images/e10-testing/partprograms/`,
+alongside the testing README. `.gitignore` blocks the path here so one cannot
+be added by accident.