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ADR 0014 phase 2, OctoSense's part: the shell's wasm service runs an app's own components. A component is an ordinary Rust crate built with cargo build --target wasm32-wasip2, or with App Flow's tools/octo wasm build. The app's script calls each function as wasm.<function> with JSON, with no glue. Stacked on #436 (phase 1, the runtime); merge that first.

What changes

• The service (crates/shell/src/wasm_service.rs):
  • It loads components from fns/ beside core modules.
  • It keeps one instance per component between calls, so a component can hold a document or a cache. A trap, the deadline, a changed grant or the worker's exit (after a minute idle) ends the instance.
  • Function names are snake_case, and either spelling is accepted.
  • The input limit is 8 MiB.
  • wasm.functions describes components: their exports with WIT signatures, and the instance's state.
• Files:
  • Where: the app's own storage folder, the jail its script's fs.* sees, is the component's /. The service decides it per call by the engines' rules (areas::app_area): none without storage, and none without a signed-in account for an app with accounts.
  • Quota, per write (crates/wasm-host/src/component/files.rs):
    • Calls that grow a file are charged against what is left of the quota.
    • Truncating and deleting give bytes back, so a component at its quota can still free space.
    • A refused write fails inside the component. Through wasi-libc it shows as an I/O error, and the call's error adds "a write was refused: the storage budget is used up".
  • Speed: file writes run on the worker's own thread.
• App Hub pin 769e9ee3 (shell: a hosted module may refuse a close and ask first (makepad#65) #186): the store admits components under wasm-components-v1.
• Runtime fixes: a one-item array is accepted as the positional arguments of a one-parameter function. The test guest gained functions that cover append, set-size and delete, and a hyphenated record and enum.
• Measurements and docs:
  • cargo run --release -p octosense-wasm-host --example measure_component measures a component against a module and native Rust.
  • ADR 0014 records the figures and the quota decision.
  • docs/wasm.md (en, zh-CN) gains a Components section.

Verified (macOS, Apple M5 Max, Rust 1.97.1)

Command	Result
cargo test --locked -p octosense-wasm-host	component 10, guest 7, runtime 14: all pass, including the storage budget (truncate refund, append, set-size, delete)
cd phone && cargo test --locked --features mobile-apps -p octosense-shell wasm_service::tests	6 pass. New: a_components_instance_keeps_state_and_its_files_stay_in_the_apps_storage (typed JSON, state, the app's folder, the quota, no folder without storage) and a_shipped_component_answers_its_apps_script (a system app through App Hub's admission).
python3 tools/setup.py --check --cargo	exit 0
The developer's flow: octo new + octo wasm new + octo wasm build (App Flow #180), the bundle shipped through admission, called as the script would	wasm.greet("Ada") → "Hello, Ada!"; wasm.count → {words: 3, lines: 2}; wasm.parse_number("two") → error "two" is not a number; wasm.calls → 1, then 2; save_note/read_note use the app's folder
measure_component	compile 37.5 ms (313 KiB), from cache 3.6 ms, instantiate 0.09 ms; Markdown → HTML 468 µs (module 400 µs, native 183 µs)

Unverified: components on a phone (Android links the same runtime, but nothing has run on a device yet), and a desktop run with a component app.

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