refactor: model bin errors as neverthrow Result values (task 0003)

Split the view command out of the entry point and make its failure a
value rather than an exception. index.ts is now scaffolding plus
dispatch; view.ts owns the behaviour, returning Result<string, ViewError>
(a plain-data tagged union) via neverthrow, with try/catch confined to a
readFile adapter. The entry point matches the Result at the boundary.

Because viewFile is a pure in-process function it is now unit-tested
directly (and counted by coverage), while the subprocess tests stay as
the end-to-end check. ADR 0008 records the errors-as-values convention.

bun.lock

@@ -21,6 +21,7 @@
         "@kitchen-md/core": "workspace:*",
         "chalk": "^5.6.2",
         "commander": "^15.0.0",
+        "neverthrow": "^8.2.0",
         "yaml": "^2.9.0",
       },
     },
@@ -60,6 +61,8 @@
 
     "@nodable/entities": ["@nodable/entities@3.0.0", "", {}, "sha512-8L9xFeTYKhm49xfIypoe2W5wV1m/3Z58kT+7kR9A8OyFxcPduI4VmxaUMQyKYrRjUoLLSXv6EKKID5Tvj9cUVw=="],
 
+    "@rollup/rollup-linux-x64-gnu": ["@rollup/rollup-linux-x64-gnu@4.62.3", "", { "os": "linux", "cpu": "x64" }, "sha512-V4KtWtQfAFMU7+9/A/VDps/VI8CHd3cYz0L8sgJzz8qK7eY7wI4ruFD82UYIYvW9Z4DtlTfhQcsl4XyPHW5uSg=="],
+
     "@types/debug": ["@types/debug@4.1.13", "", { "dependencies": { "@types/ms": "*" } }, "sha512-KSVgmQmzMwPlmtljOomayoR89W4FynCAi3E8PPs7vmDVPe84hT+vGPKkJfThkmXs0x0jAaa9U8uW8bbfyS2fWw=="],
 
     "@types/mdast": ["@types/mdast@4.0.4", "", { "dependencies": { "@types/unist": "*" } }, "sha512-kGaNbPh1k7AFzgpud/gMdvIm5xuECykRR+JnWKQno9TAXVa6WIVCGTPvYGekIDL4uwCZQSYbUxNBSb1aUo79oA=="],
@@ -168,6 +171,8 @@
 
     "ms": ["ms@2.1.3", "", {}, "sha512-6FlzubTLZG3J2a/NVCAleEhjzq5oxgHyaCU9yYXvcLsvoVaHJq/s5xXI6/XXP6tz7R9xAOtHnSO/tXtF3WRTlA=="],
 
+    "neverthrow": ["neverthrow@8.2.0", "", { "optionalDependencies": { "@rollup/rollup-linux-x64-gnu": "^4.24.0" } }, "sha512-kOCT/1MCPAxY5iUV3wytNFUMUolzuwd/VF/1KCx7kf6CutrOsTie+84zTGTpgQycjvfLdBBdvBvFLqFD2c0wkQ=="],
+
     "path-expression-matcher": ["path-expression-matcher@1.6.2", "", {}, "sha512-enSlaiat05iasnzmgNxRj8reFdj3puY2QpNgP1aPIaVfT6nn9ICuPoFlKHk8EN22HcwewshO+mN2DGbkCEOtqQ=="],
 
     "remark-frontmatter": ["remark-frontmatter@5.0.0", "", { "dependencies": { "@types/mdast": "^4.0.0", "mdast-util-frontmatter": "^2.0.0", "micromark-extension-frontmatter": "^2.0.0", "unified": "^11.0.0" } }, "sha512-XTFYvNASMe5iPN0719nPrdItC9aU0ssC4v14mH1BCi1u0n1gAocqcujWUrByftZTbLhRtiKRyjYTSIOcr69UVQ=="],