fix(core): keep stdout pure when -o json/yaml/csv is requested

[GregHolmes]

Closes #98. Branched off main, independent of the other open PRs.

The bug

Commands print status lines and human tables for people; the framework writes the serialised result to stdout. Under a machine-readable format both went to the same stream:

$ dg -o json projects | jq .
Fetching projects...        # stdout
Found 1 project(s):         # stdout
{ ... }                     # stdout, too late for jq

The payload was never missing — just buried. In dg -o json models the JSON started 37 KB into stdout, behind a Rich table.

Status routing keyed off agentic (a TTY/env heuristic) rather than "does something else own stdout", so an explicit -o json on a terminal still sent status to stdout. listen and speak escaped because they gate their own display on the format; the other eight commands didn't.

The fix

• StatusConsole resolves its write target at write time: stderr when the active format is in MACHINE_FORMATS (json/yaml/csv), stdout otherwise. The shared console is one, so print_info/print_success/print_warning/print_panel/print_separator follow automatically.
• stdout_console carries the payload; print_output now uses it, so the result is never diverted along with the status text.
• get_status_console() replaces the private Console() in the eight affected commands — a one-line change each.

table is deliberately not a machine format: it's a human rendering and keeps stdout.

What I deliberately did not do

Wrapping handle() in redirect_stdout would have been a smaller diff, but dg speak streams audio through sys.stdout.buffer.write() and branches on sys.stdout.isatty() — a blanket redirect would corrupt piped audio and flip that branch. Routing at the console layer leaves sys.stdout untouched.

Verification

check	result
dg -o json {models,projects,keys,usage,billing,requests,members,read}	stdout parses as JSON ✓ (was polluted)
-o yaml / -o csv	valid YAML ✓ / CSV header ✓
dg speak "..." | ffplay	RIFF/WAV stream, no JSON mixed in ✓
dg -o json listen f.mp3 | jq	unchanged ✓
human output in a real pty	unchanged; status still on stdout ✓
-o json in a pty	payload on stdout, status on stderr ✓
unit tests	1059 passed, 6 skipped (7 new regression tests)
live API smoke suite	68/68 ✓

The 5 print_output tests that asserted it writes via console were repointed to stdout_console — that coupling is precisely what this change fixes.

Note for review

Three files (output.py, projects/command.py, usage/command.py) are stored with CRLF line endings. My first pass normalised them to LF and ballooned the diff to ~1300 lines; I restored their original convention, so the diff is now 127 insertions / 31 deletions. Worth considering a .gitattributes to settle line endings repo-wide — mixed conventions make diffs like that easy to create by accident.

[GregHolmes]

Superseded by #101 — closing.

#97 landed the per-command pattern (status_console for chrome, human rendering gated on get_output_format() == "default") across seven commands, so the central format-aware console here would now conflict with main rather than complement it. #101 finishes the sweep for keys, the one command #97 missed.

The idea from this PR worth keeping — a shared primitive rather than a Console(stderr=True) declared per command — is in #101 as get_status_console() in core, with all eight commands migrated to it.