feat(build): slim txiki.js runtime — binary 6.4 MB → 2.4 MB, v0.9.0

[lukasMega]

What

Ships the slim-ffi txiki.js runtime from lukasMega/txiki.js-with-slim-builds@slim-v26.6.0-6 (txiki.js v26.6.0) on every platform, and bumps to 0.9.0 (merging this fires auto-tag → release).

Profile keeps tjs:ffi, WebCrypto, run/compile, REPL. Drops TLS, WebAssembly, SQLite, mimalloc and the eval/serve/test/bundle/app subcommands; MinSizeRel + compressed bytecode + hardened + stripped.

TLS costs ~430 KB and buys nothing here — every fetch() in the repo runs in the browser UI, not the runtime.

Size (macOS arm64)

runtime	tjs	compiled deckbridge
old prebuilt v26.5.1	5.7 MB	6,690,315 B (6.4 MB)
slim-ffi (downloaded)	2.0 MB	2,481,492 B (2.4 MB)
slim-ffi (from source)	1.93 MB	2,448,665 B

Packaged .tar.xz: 1.9 MB.

Changes

• scripts/tjs-download.mjs — fetches txiki-slim-ffi-<os>-<arch>.zip. macOS x86_64 has no such asset → explicit error pointing at TJS_FROM_SOURCE=1.
• scripts/tjs-build.mjs — stops hand-rolling cmake flags; clones the tag and runs the fork's own scripts/build-dist.mjs --profile ffi (the same driver that builds the published assets). Now also no-ops when $TJS exists — which is what the release workflow's runtime cache always assumed, so local mise run test drops from ~120 s to ~20 s.
• release.yml — only macos-x86_64 builds from source now (TJS_FROM_SOURCE comes from the matrix); everything else downloads. Linux release builds re-enabled (linux-x86_64, linux-arm64): the blocker was mise-action blind-installing the github:lukasMega/txiki.js mise tool that had no linux-arm64 asset — that tool entry was unused and is now deleted.
• mise.toml — one version var instead of two; dead tool/hook blocks gone; per-task re-exports of vars mise already exports gone; rust-fmt/rust-clippy/rust-test, run-ts, largeFiles dropped as verbatim duplicates of rust-lint/s/loc; checkTjs no longer calls $TJS --help (slim compiles help out). 371 → 320 lines.

Verified locally (macOS arm64)

• Downloaded binary's sha256 matches the release's published BUILDINFO.
• Full tjs test suite green on both the downloaded and the from-source slim runtime.
• From-source path green end-to-end (2,026,944 B, inside upstream's budget).
• Compiled binary mock-boots: web UI 200, CORA 5343 + 5344 listening, FFI dlopen of libhidapi/libdeckbridge_native OK.
• Packaged artifact extracted and booted standalone; /api/state OK.
• Startup time unchanged (0.04–0.05 s per test run across all three runtimes).

Untested

Windows (now gets slim via the download path) and the Linux matrix — both are CI-only paths. fail-fast is off, so a Linux failure wouldn't block the other platforms' artifacts.