v0.50.0

Release Notes — v0.50.0

Minor: Read every part of a file you need in one call

An agent that had found five places to look in a file used to spend five
calls reading them. Each call returned one window, and each of those windows
was sent back to the model again on the next step of the turn.

read now takes ranges, a list of {start_line, end_line} windows. One
entry is one region; several read every hit at once, in the order asked, each
under its own file:start-end heading and with the same numbered lines an
edit copies from. The ranges a file_map prints and the lines a search
found can be read together. The byte budget spans the whole call, so no window
can spend another's, and a window that got no room is named rather than
quietly dropped.

The top-level start_line/end_line pair is no longer a second spelling of
the same thing. It is refused by name rather than ignored, because an argument
that is silently dropped reads the file from the top and says nothing about
doing so, and an ignored end_line reads past the line that was meant.
Combining ranges with offset/limit is refused for the same reason: they
are two ways of placing a window, and only one of them can be meant.

Minor: A turn reports what it cost the machine

Ogcode reports a handful of events so the project can tell how it is being
used. One that was missing is the most direct question you can ask of an agent
doing real work on your machine: what did that turn cost?

Every turn you asked for — a build, a plan, a note, a task — now reports a
resource event when it ends: how long it took, how much of that was measured,
the process's resident memory and its peak, average and peak CPU, goroutine
counts, and the cores and memory of the machine. Collection stops while
nothing watches it, so the turn holds a measurement for its own length, and
the figure is reported whichever way the turn returns — a clean finish, a
step limit, an abort, or an error. Work that runs inside a turn, such as a
sub-agent or a memory recall, is not counted separately, so one turn is one
row.

The values describe the whole process rather than one turn's share of it, and
they carry counts and durations only — never the content of your work.

Other changes

• The file_map description, the memory_map header and the codemap
  renderer all name the ranges form, so an agent is told how to read a
  window everywhere it is told to read one.
• A truncated read now ends by naming the form that would have read more of
  the file at once — the moment a caller decides whether to read again.
• HOWTO.md records the install command that keeps the gateway secret out of
  make's echoed recipe, and the benchmark recipe for an offline run with a
  reused code index.