feat(gust): E2 — the whole OS dissolves, and the seam survives it

[avrabe]

v0.6.0 shipped the composed OS as 20 741 bytes and said plainly that this was a wasm figure implying nothing about code size, SRAM or cycles. build-fused-gustos.sh carried the same caveat in its own header — "NOT done here: lowering the composite to native." It is done here.

The result

fused-gustos.component.wasm  20741 B (wasm component)
  -> meld fuse --memory shared -> loom optimize --passes inline
  -> synth compile --target cortex-m3 --all-exports --relocatable

text 4792   data 0   bss 0     0 B of the STM32F100RB's 8192 SRAM
31 functions · 25 import-call relocations · 3 external symbols

Pinned to synth 0.52.0 (#208) rather than PATH, so the figure is comparable to what is already recorded rather than to whatever happens to be installed.

The gate, and its direction

undefined (3): poll-task read32 write32
               ^taskdisp  ^gust:hal/mmio

Two ways to fail, and the second is the one worth stating:

• more than that — the OS depends on something we never declared;
• an empty set — the seam was inlined away. That yields a smaller object and reads like a win, but an OS whose hardware seam has been swallowed is no longer swappable, which is the whole thesis. Exit 2.

The negative control bites, on every run. wasm-kernel/fused.wasm lowers with zero undefined symbols — exactly the seam-swallowed shape — and the gate refuses it. If that control ever passes, the script exits 4, because a gate that has stopped discriminating reports a green that means nothing. #254 is why this lives in the script rather than in my head.

Not claimed

Stated in measurements/composite-dissolved.md rather than left to be assumed:

• 20 741 → 4 792 is not a ratio. A wasm component carrying component metadata and a .text section measure different things. Quoting it as compression is the exact conflation loom-across-the-fuse.md already had to correct once in this repo.
• bss 0 is zero static allocation in the object, not "the OS needs no RAM" — stacks and any arena come from the embedder.
• Relocatable object, not a linked image. It still needs the TCB bridge; synth says so itself.
• Not executed. E1 ran the component on a host engine; nothing has run this object. Renode is E3, silicon E4 — both v0.7.1.

Status

REQ-OS-COMPOSITE-DISSOLVE-001 → implemented, deliberately not verified: nothing in CI runs this yet, so the property can still silently stop holding. That is what VER-OS-COMPOSITE-DISSOLVE-001 asks for, and CI has an established pinned-toolchain pattern (release-wasm.yml) to copy — next commit.

What it unblocks

E2 was the critical path for everything left in v0.7.0:

	was blocked because	now
REQ-OS-OBJVERIFY-001 (T2)	no object to verify	has one
REQ-OS-WCET-001 (T4)	nothing to bound	31 named functions
REQ-OS-SCHED-001 (T3)	consumes T4's numbers	moves when T4 does

rivet validate: PASS, 333 warnings, unchanged.

[codecov]

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