v0.1.0-rc1

Added

• Initial implementation of herescript as a single-file C program (herescript.c).
• Shebang-based launcher: scripts begin with #!/usr/bin/herescript <executable>,
  where <executable> is bound to ${HERESCRIPT_COMMAND}.
• Three new header line types that cleanly replace the legacy #!-prefix approach:
  • ## — comment line, discarded entirely.
  • #: — arguments and bindings line, parsed with shell-like tokenisation.
  • #> — inline quoted argument line; a bare #> or one not followed by a
    space is a syntax error.
• Shell-like tokenisation on #: lines, supporting:
  • Runs of whitespace as token separators.
  • '...' — plain single-quoted literals (no escapes, no substitution).
  • $'...' — escape-quoted single-quoted strings; supports \\, \', \",
    \n, \r, \t, \s.
  • "..." — double-quoted strings with variable interpolation and minimal
    backslash escapes (\\, \", \$).
  • $"..." — escape-quoted double-quoted strings (full backslash escape
    expansion as per $'...', plus variable interpolation).
• Variable and parameter substitution inside #: lines and double-quoted spans:
  • ${NAME} — expands to the value of the named environment variable; exits
    with an error if undefined.
  • ${N} — expands to the N-th user-supplied argument (${0} is the
    canonicalised script path, synonymous with ${HERESCRIPT_FILE}).
  • ${A:B} — parameter slice; expands to the arguments from index A up to
    (but not including) B, each as a separate token. A and B default to 0 and
    argc respectively when omitted. $@ is a synonym for ${1:}.
  • ${:} — expands to ${HERESCRIPT_FILE} followed by all user-supplied
    arguments; provided as a convenient default invocation.
  • ${HERESCRIPT_FILE} — the canonicalised path of the running script.
  • ${HERESCRIPT_COMMAND} — the executable named on the #! line.
  • ${NAME-VALUE} — expands to VALUE when NAME is unset; otherwise
    expands to the current value of NAME.
  • ${NAME:=VALUE} — equivalent to ${NAME-VALUE}; mirrors the #: binding
    syntax to reduce cognitive load.
  • $NAME — bare unbraced identifier; greedily consumes [a-zA-Z_][a-zA-Z0-9_]*.
  • $N… — bare unbraced digit run; greedily consumes all consecutive digits,
    so $10 expands parameter 10.
• Environment variable bindings on #: lines:
  • NAME=VALUE — unconditionally sets NAME in the child environment.
  • NAME:=VALUE — sets NAME only when it is not already defined in the
    environment (conditional initialisation).
  • Bindings are recognised only as leading tokens; quoting the name or
    separator suppresses binding recognition and treats the token as a plain
    argument.
• Inline quoted arguments via #> lines:
  • A run of consecutive #> lines is glued together (preserving embedded
    newlines) and bound to ${HERESCRIPT0}, ${HERESCRIPT1}, etc.
  • A #: line between two #> runs forces a break, starting a new argument.
• Executable lookup via PATH when the shebang does not specify an absolute path.