fix(nix): move the bun packages to bun2nix — no more hand-bumped deps hash

`nix build .#punktfunk-web` has been broken since 1e9957d9 re-resolved
web/bun.lock: the console's node_modules came from a fixed-output derivation
whose single aggregate `outputHash` was last refreshed in 4094f620, so every
lockfile change silently invalidated it and the fix required a round-trip on a
Linux nix box (build, read the `got:` hash, paste it back). The runner
(sdk/bun.lock) had the same latent trap.

Replace both FODs with bun2nix (github:nix-community/bun2nix, pinned to 2.1.2).
`fetchBunDeps` turns a generated, committed `bun.nix` into bun's global install
cache — ONE `fetchurl` per package, keyed by the integrity hash already in the
lockfile — and the setup hook then runs a fully offline `bun install` in
`bunRoot`. There is no aggregate hash left to go stale. The `@unom` scope needs
no special handling: bun.lock records those tarballs' full git.unom.io URLs and
the registry is read-public.

`bun.nix` keeps itself in step: `bun2nix` is now a devDependency of both
packages and regenerates the file on every `bun install` — web via
`postinstall`, the SDK via `prepare`, because sdk/ is the published
@punktfunk/host package and a postinstall would fire on consumers' installs.
Both the flake input and the npm devDependency are pinned to the same exact
version; `bun.nix` has no schema stability guarantee across bun2nix releases, so
they move together (README documents this).

Dropped along the way: the manual `cp -R ${deps}/node_modules` + `chmod -R u+w`
+ `patchShebangs web/node_modules` dance, since bun2nix patches shebangs inside
the cache. `dontUseBunPatch` keeps the hook from running `patchShebangs .` over
the whole repo checkout (it would rewrite scripts/web-init.sh, which we ship
verbatim); `dontRunLifecycleScripts` preserves the old `--ignore-scripts`
behaviour, so playwright still never tries to download browsers.

Verified on a Linux nix box (Determinate Nix 3.21.5): `.#punktfunk-web` and
`.#punktfunk-scripting` both build green, offline; the i18n guard reports its
421 compiled messages, the `Bun.serve` bundle guard passes, and
`nix run .#punktfunk-scripting -- --list` discovers an installed plugin.
`nix flake show --all-systems` evaluates every output.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
(cherry picked from commit 4cfe7f05ee608868857be9e7eec079044448a965)

sdk/bun.lock

@@ -8,6 +8,7 @@
         "@effect/openapi-generator": "4.0.0-beta.98",
         "@effect/platform-node": "4.0.0-beta.98",
         "@types/bun": "^1.3.0",
+        "bun2nix": "2.1.2",
         "effect": "^4.0.0-beta.98",
         "typescript": "^5.9.3",
       },
@@ -56,6 +57,8 @@
 
     "bun-types": ["bun-types@1.3.14", "", { "dependencies": { "@types/node": "*" } }, "sha512-4N0ig0fEomHt5R0KCFWjovxow98rIoRwKolrYdCcknNwMekCXRnWEUvgu5soYV8QXtVsrUD8B95MBOZGPvr6KQ=="],
 
+    "bun2nix": ["bun2nix@2.1.2", "", { "dependencies": { "sade": "^1.8.1" }, "bin": { "bun2nix": "index.ts" } }, "sha512-0wx6Ar5ccrz4aSD5prbShwymjDEXFh7Bucxs+YrpAMa67TnVB95Hv8FV3oaQEbtOx6QGgIAyOmap6Y3WCRqetg=="],
+
     "call-me-maybe": ["call-me-maybe@1.0.2", "", {}, "sha512-HpX65o1Hnr9HH25ojC1YGs7HCQLq0GCOibSaWER0eNpgJ/Z1MZv2mTc7+xh6WOPxbRVcmgbv4hGU+uSQ/2xFZQ=="],
 
     "cliui": ["cliui@8.0.1", "", { "dependencies": { "string-width": "^4.2.0", "strip-ansi": "^6.0.1", "wrap-ansi": "^7.0.0" } }, "sha512-BSeNnyus75C4//NQ9gQt1/csTXyo/8Sb+afLAkzAptFuMsod9HFokGNudZpi/oQV73hnVK+sR+5PVRMd+Dr7YQ=="],
@@ -100,6 +103,8 @@
 
     "mime": ["mime@4.1.0", "", { "bin": { "mime": "bin/cli.js" } }, "sha512-X5ju04+cAzsojXKes0B/S4tcYtFAJ6tTMuSPBEn9CPGlrWr8Fiw7qYeLT0XyH80HSoAoqWCaz+MWKh22P7G1cw=="],
 
+    "mri": ["mri@1.2.0", "", {}, "sha512-tzzskb3bG8LvYGFF/mDTpq3jpI6Q9wc3LEmBaghu+DdCssd1FakN7Bc0hVNmEyGq1bq3RgfkCb3cmQLpNPOroA=="],
+
     "ms": ["ms@2.1.3", "", {}, "sha512-6FlzubTLZG3J2a/NVCAleEhjzq5oxgHyaCU9yYXvcLsvoVaHJq/s5xXI6/XXP6tz7R9xAOtHnSO/tXtF3WRTlA=="],
 
     "msgpackr": ["msgpackr@2.0.4", "", { "optionalDependencies": { "msgpackr-extract": "^3.0.4" } }, "sha512-o1C5KRmuRt+apqMr1HuGSqWStZoRBUpEsCsl15uM9VdAF1qHLtvMOU2En747EnTyEl6c4pzPewRMFF31s1CNbA=="],
@@ -136,6 +141,8 @@
 
     "require-directory": ["require-directory@2.1.1", "", {}, "sha512-fGxEI7+wsG9xrvdjsrlmL22OMTTiHRwAMroiEeMgq8gzoLC/PQr7RsRDSTLUg/bZAZtF+TVIkHc6/4RIKrui+Q=="],
 
+    "sade": ["sade@1.8.1", "", { "dependencies": { "mri": "^1.1.0" } }, "sha512-xal3CZX1Xlo/k4ApwCFrHVACi9fBqJ7V+mwhBsuf/1IOKbBy098Fex+Wa/5QMubw09pSZ/u8EY8PWgevJsXp1A=="],
+
     "should": ["should@13.2.3", "", { "dependencies": { "should-equal": "^2.0.0", "should-format": "^3.0.3", "should-type": "^1.4.0", "should-type-adaptors": "^1.0.1", "should-util": "^1.0.0" } }, "sha512-ggLesLtu2xp+ZxI+ysJTmNjh2U0TsC+rQ/pfED9bUZZ4DKefP27D+7YJVVTvKsmjLpIi9jAa7itwDGkDDmt1GQ=="],
 
     "should-equal": ["should-equal@2.0.0", "", { "dependencies": { "should-type": "^1.4.0" } }, "sha512-ZP36TMrK9euEuWQYBig9W55WPC7uo37qzAEmbjHz4gfyuXrEUgF8cUvQVO+w+d3OMfPvSRQJ22lSm8MQJ43LTA=="],