Look and Exec are builtins like any other

Their only special feature is now the keys they are assigned. `Look main.zig`
typed in a tag is the same look a right click is; config.look_cmd/exec_cmd
point the two buttons and Enter/Tab at them, so retargeting Enter to Grep is
one line. actOnSelection — a hand-written cascade with the builtin dispatch
nested inside it — is gone, and the `button` parameter it threaded through five
KEYBOARD call sites went with it.

New syntax, spelled once in config.zig: @`ls -la` names a command to run
rather than a file to open. Word expansion takes the quoted run whole, the way
acme does for its own </|/> words, so a click inside one does not hand Look the
fragment `ls`.

And it nests: @`Look .` unwraps, re-enters the dispatcher, and looks at the
directory. Guarded at depth 8, which is unreachable today (every re-entry
strips a word or a delimiter pair, so the string strictly shrinks) and exists
for a future syntax that does not shrink.

leader_path is now optional: a builtin may have no SPC path when its shortcut
is a key and a mouse button. New golden cmdword; the other 59 unmoved.

0 files changed, 0 insertions, 0 deletions