Canonical source formatting

sprig fmt file.spr formats a file in place. sprig fmt . formats the current project's declared source tree (default src/), or the selected directory when no project/source tree exists. sprig fmt --check file.spr writes nothing and returns 1 if changes are needed. Both commands accept --json, using the standard diagnostic envelope plus checkedFiles, changedFiles and checkOnly.

The formatter uses four spaces per block, one space around binary operators, commas followed by a space, and no spaces inside delimiters. Inline comments are separated by two spaces; standalone comments retain their physical order and indentation relative to the surrounding block. Repeated blank lines are reduced to one. Strings and numeric literal spellings are preserved exactly. It is deterministic and idempotent, with no configuration, style flags or aggressive wrapping. Explicit invocation is the only way source is rewritten.

Source must parse first. Tabs remain invalid. All selected files are validated before any writes, and each changed file is replaced atomically beside the original, preserving POSIX permissions. Parse/format failure writes nothing; I/O failure may occur after other files have been replaced, so this is not a transaction spanning multiple files. Symbolic link replacement is refused.

Spaces and comments are lexer hidden-channel tokens. The layout adapter uses only default-channel tokens; formatter trivia never enters semantic AST nodes. Formatting is checked against the original parse-rule/terminal structure, ignoring source locations. This prevents changes in operator grouping and block structure. It does not execute or type-check a module to format it.

Continuation lines inside delimiters receive one extra indentation level. There is no line wrapping or alignment algorithm. Ambiguous standalone comment association follows its original column and surrounding indentation stack; comments are never reordered or deleted.