docs(requirements): split generated fact inference rule

Split oversized canonical_authoring/004 into known-template-facts and explicit-diagnostic requirements.

req: canonical_authoring/004

req: canonical_authoring/016

AGENTS.md

@@ -57,7 +57,7 @@ Keep it stable. Prefer pointers to canonical sources over copied structure, file
 - Use the same Workout command surface for tests, production build, and mobile release: `cargo run -p hemx-xtask -- workout test`, `cargo run -p hemx-xtask -- workout build`, `HEMX_WORKOUT_ORIGIN=https://workout.example.com cargo run -p hemx-xtask -- workout mobile-release`, and `HEMX_WORKOUT_ORIGIN=https://workout.example.com cargo run -p hemx-xtask -- workout mobile-verify`; Android/iOS SDKs, store submission targets, and signing remain external blockers, not repo-owned secrets. req: examples/006 req: examples/011
 - hemx core stays small: effects, typed ids, registries, and wire schema only.
 - Routing, auth, sessions, transport, transitions, sync, and storage belong in integration/user crates.
-- Public examples and beginner APIs should use templates plus Rust, generated resources, and `IntoEffect`, not raw ids, selectors, wire formats, or runtime opcodes. req: canonical_authoring/001 req: canonical_authoring/006 req: canonical_authoring/010 req: canonical_authoring/015
+- Public examples and beginner APIs should use templates plus Rust, generated resources, and `IntoEffect`, not raw ids, selectors, wire formats, or runtime opcodes. req: canonical_authoring/001 req: canonical_authoring/004 req: canonical_authoring/006 req: canonical_authoring/010 req: canonical_authoring/015
 - Typed partial swaps should stay expressed as generated target plus rendered partial plus swap kind, not selector-driven rerendering. req: canonical_authoring/002 req: canonical_authoring/014
 - `examples/html_examples` is the copy-paste HTML pattern gallery for htmx-style examples; keep exact htmx URL slugs visible while translating behavior to boring `.heml`, generated resources, and server-owned Rust state. req: htmx_equivalents/001 req: htmx_equivalents/005 req: examples/007
 - Use `cargo run -p hemx-xtask -- app new PATH` for the generic page/form/keyed-row/notice starter, and `cargo run -p hemx-xtask -- app new --mobile PATH` for the phone-first starter with host capabilities, recovery truth, and release-kit commands. req: ceremony/005 req: ceremony/006

REQUIREMENTS.md

@@ -71,7 +71,10 @@ client app state framework.
 015	Summary, text, and form effects compose in tuples, arrays, or `Vec<T: IntoEffect>` for dynamic batches, and no handler chooses a target with a CSS selector. [north_star]
 
 ### req: canonical/004
-004	Generated helpers may compose only facts uniquely known from templates and checked Rust types: template, slot, optional key, form/control, class token, explicit island/event marker, and effect kind. If a handler parameter, key, form, target, raw route, or legacy target would require guessing, the user must say it explicitly and diagnostics must point to the Rust and hemplate spans. [north_star]
+004	Generated helpers may compose only facts uniquely known from templates and checked Rust types: template, slot, optional key, form/control, class token, explicit island/event marker, and effect kind. [north_star]
+
+### req: canonical/016
+016	If a handler parameter, key, form, target, raw route, or legacy target would require guessing, the user must say it explicitly and diagnostics must point to the Rust and hemplate spans. [north_star]
 
 ### req: canonical/005
 005	Generated helpers name UI intent without mixing domain work: target helpers read as UI effects such as `replace`, `append`, `remove`, `set`, `clear`, `focus`, `set_attr`, or `emit` on generated page, slot, form, class, attribute, or island handles. [north_star]