fix(cli): a query is not a path, and a dash is not a flag (#178)

Two ways a correct search died before searching:

Bug A — a query containing '/' alongside -e. The path-vs-query heuristic
treated any slash-bearing query as a misplaced PATH argument, so
  colgrep 'proxy auth on retries/redirects' -e Client -k 10
hard-errored with 'Path does not exist'. The reclassification now fires
only when the token could really be a path: it exists on disk, or it is
a whitespace-free path-shaped token (kept so a mistyped ./sr still gets
the path error instead of silently becoming a search).

Bug B — a query starting with '-'. The query positional rejected hyphen
values, so
  colgrep '--glob flag option' -k 5
aborted with 'unexpected argument'. Both query positionals now take
allow_hyphen_values; defined flags still parse as flags, and the '--'
separator still works. The trade-off: a mistyped long flag becomes a
search instead of an error — right for a tool whose callers include
agents emitting queries about flags.

Unit tests cover both parses and the classifier; a 22-case stress
battery (slashes, leading dashes, --, quotes, unicode, newlines, long
queries, path-typo error preservation) passes against a live index.