Add create-type, retype, and sync to the decompiler CLI

[mahaloz]

Feature 1 (retyping):

• create-type "<C def>" parses a C struct/enum/typedef into a libbs artifact (new libbs/api/type_definition_parser.py, pycparser-based with natural-alignment offsets) and applies it across any backend.
• retype <func> <var> <type> sets a local variable's or argument's type.

Feature 2 (syncing):

• sync <func> --from-id <src> [dest filters] copies a function's name, return/arg types, stack-variable names+types, and referenced user types from one running server into another for the same binary. Addresses and stack offsets are canonical, so artifacts re-key across decompilers.

Underlying fixes required for cross-decompiler (IDA->Ghidra) sync:

• ghidra headless: force -Djava.awt.headless=true so a stale DISPLAY no longer crashes the JVM with an X11 AWTError.
• Function.setstate: initialize the dec_obj slot so access after a deserialization round-trip (get_dependencies, rename) doesn't raise.
• IDA headless DummyIDACodeView: implement real set_lvar_type/rename_lvar via modify_user_lvar_info/rename_lvar so retypes persist headlessly.
• ghidra typestr_to_gtype: resolve a pointer-to-user-struct (e.g. "Point *") by building the pointer from the looked-up base type.

Tests (tests/test_decompiler_cli.py): parser unit tests, create-type/retype across angr/Ghidra/IDA, and IDA->Ghidra sync of both names and types. SKILL.md documents the three new commands.

Demo