* feat: add host-callback channels to library mode
- the profile's `callbacks` array declares named channels and
`abi.callback_register_symbol` names the one registration entry point:
`int32_t <sym>(const char *name, void (*fn)(void), void *ctx)` — 0 on
success, -1 for an unknown or NULL name, latest registration wins, a
NULL fn clears, registrations persist across init/reset. The stored
pointer's typed shape is the channel's with the opaque context first,
the panic sink's layout
- channel signatures ride the existing marshalling classes: params are
f64/bool/string/bytes plus the u8/u32/i32 plumbing classes (outbound
plumbing keeps JS's ToUint32/ToInt32, the executable FFI rule);
returns are scalar only (f64/bool/u8/u32/i32/void — a buffer return
needs an ownership contract the mode does not define). string/bytes
parameters arrive as (ptr, len) pairs borrowed for the call's duration
- compiled code reaches a channel as a signature-only ambient function
declaration whose direct calls deliver synchronously on the calling
thread; the recognition rides the FFI import machinery under a library
flavor: SC4024 refuses a call the channels cannot serve (undeclared
name or off-class signature), unused channels are legal capacity, and
callback-free profiles keep the ambient ReferenceError semantics
- calling an unregistered channel is the SC4025 runtime trap: a detected
trap through the library funnel, so the structured sink message names
the channel in its text and the entry the host called in its symbol
field, and profile teachings/remediations overlay it like the rest of
the runtime family
- registration slots are per copy of the runtime state, the sink's story:
per-archive under abi.localize_runtime (the register symbol joins the
localization keep-list), per-thread instance under
abi.instance_per_thread. The host callback must not reenter any library
entry or unwind across library frames
- both emissions produce identical behavior by construction: the slot
store/fetch lives in scr_library.c (scr_library_cb_set/_require/_ctx),
the generated TU emits the registration dispatch and typed indirect
calls, and the trap text is assembled once at export resolution
- callback-free profiles emit byte-identical program TUs and serialized
IR, and executable builds are byte-identical end to end
- conformance: the CB suite (tests/harness/library-callbacks.test.ts)
covers the acceptance stream, unregistered and pre-registration traps,
symbol exactness, teaching overlays, SC4024 refusals, capacity and
callback-free postures, the localized+thread-instanced composition
probe, and ASan reruns; profile-shape refusals join
library-profile.test.ts
* fix: preserve callback binding identity
* fix: harden library callback contracts
* fix: recognize project callback declarations
* fix: enforce host callback declarations
