fix(opencode): the 2.x home placeholder is not typed input, cut example included (Issue #60, Linux item 1)

An adapter can now name its placeholder as a pattern the box's first line
matches in full (input_placeholder_pattern); input_placeholder stays the
literal lib.sh greps for. opencode: `Ask anything… "<example>"`, the closing
quote optional because a box under ~65 columns cuts the example. Fixtures:
the 140-column herdr capture and a 60-column one with the cut example.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/fixtures/panes/opencode_idle_2x_home.txt

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+# captured 2026-10-18 from an idle opencode 2.0.32 home screen (no message sent), input box empty: herdr 0.9.3 `herdr agent read <session> --source visible`, 140x40 (cwd line masked)
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+                                                                         ▄
+                                        █▀▀█ █▀▀█ █▀▀█ █▀▀▄ █▀▀▀ █▀▀█ █▀▀█ █▀▀█
+                                        █  █ █  █ █▀▀▀ █  █ █    █  █ █  █ █▀▀▀
+                                        ▀▀▀▀ █▀▀▀ ▀▀▀▀ ▀▀▀▀ ▀▀▀▀ ▀▀▀▀ ▀▀▀▀ ▀▀▀▀
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+
+                      ┃
+                      ┃  Ask anything… "Fix a TODO in the codebase"
+                      ┃
+                      ┃  Build auto · Nemotron 3.5 Super VL Free OpenCode
+                      ╹▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀
+                      /…/<repo>/<worktree>:<branch>    shift+tab agents  ctrl+p commands
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+                                                                                                               2.0.32

tests/fixtures/panes/opencode_idle_2x_home_narrow.txt

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+# captured 2026-10-18 from an idle opencode 2.0.32 home screen (no message sent), input box empty, width 60: tmux 60x30 `capture-pane -p`; the example is cut without its closing quote (cwd line masked)
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+                                            ▄
+           █▀▀█ █▀▀█ █▀▀█ █▀▀▄ █▀▀▀ █▀▀█ █▀▀█ █▀▀█
+           █  █ █  █ █▀▀▀ █  █ █    █  █ █  █ █▀▀▀
+           ▀▀▀▀ █▀▀▀ ▀▀▀▀ ▀▀▀▀ ▀▀▀▀ ▀▀▀▀ ▀▀▀▀ ▀▀▀▀
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+  ┃
+  ┃  Ask anything… "What is the tech stack of this proje
+  ┃
+  ┃  Build · Nemotron 3.5 Super VL Free OpenCode
+  ╹▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀
+  /…/<worktree>:<branch>  shift+tab agents  ctrl+p commands
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tests/test_issue60_linux_fixes.py

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+"""Issue #60, Linux check: the defects the opencode 2.x check on Linux found.
+
+1. The 2.x home screen's placeholder (`Ask anything… "<example>"`, cut
+   without its closing quote in a narrow box) is not typed input.
+"""
+
+from __future__ import annotations
+
+import re
+import sys
+from pathlib import Path
+
+import pytest
+
+REPO_ROOT = Path(__file__).resolve().parent.parent
+SKILLS = REPO_ROOT / ".agents" / "skills"
+PANES = REPO_ROOT / "tests" / "fixtures" / "panes"
+if str(SKILLS) not in sys.path:
+    sys.path.insert(0, str(SKILLS))
+
+from lib_py import stall_watch  # noqa: E402
+from lib_py.agents.input_region import extract_input_region  # noqa: E402
+from lib_py.agents.registry import get_adapter  # noqa: E402
+
+# 140 columns (herdr capture) and 60 columns, where the example loses its
+# closing quote.
+HOME_SCREENS = ("opencode_idle_2x_home.txt", "opencode_idle_2x_home_narrow.txt")
+PLACEHOLDER_LINE = re.compile(r'^(\s*┃\s*)Ask anything… ".*$', re.M)
+
+
+def _pane(name: str) -> str:
+    return "".join(l for l in (PANES / name).read_text(encoding="utf-8").splitlines(True) if not l.startswith("# "))
+
+
+# ---------------------------------------------------------------------------
+# 1. the 2.x home screen's placeholder
+# ---------------------------------------------------------------------------
+@pytest.mark.parametrize("name", HOME_SCREENS)
+def test_the_2x_home_screen_reads_as_an_empty_box(name):
+    assert extract_input_region(_pane(name), "opencode") == ""
+
+
+def test_the_narrow_capture_has_a_cut_example():
+    # The case the pattern must keep: no closing quote on screen.
+    (line,) = [l for l in _pane(HOME_SCREENS[1]).splitlines() if "Ask anything" in l]
+    assert '"' in line and not line.rstrip().endswith('"')
+
+
+def test_the_narrow_screen_stops_at_its_status_line_and_reads_ready():
+    text = _pane(HOME_SCREENS[1])
+    # Under ~60 columns the status line drops `auto`: `Build · <model>`.
+    assert re.search(r"^\s*┃\s*Build · ", text, re.M) and "Build auto" not in text
+    assert re.search(get_adapter("opencode").ready_tokens, text)
+
+
+@pytest.mark.parametrize("name", HOME_SCREENS)
+@pytest.mark.parametrize("typed", [
+    "please continue",
+    'Ask anything… "x" and fix it',
+    "Ask anything about the build",
+    'Ask anything… "a"b',
+])
+def test_typed_text_is_read_as_typed(name, typed):
+    text, n = PLACEHOLDER_LINE.subn(lambda m: m.group(1) + typed, _pane(name), count=1)
+    assert n == 1
+    assert extract_input_region(text, "opencode") == typed
+
+
+def test_the_1x_capture_still_reads_empty():
+    assert extract_input_region(_pane("opencode_idle.txt"), "opencode") == ""
+
+
+@pytest.mark.parametrize("name", HOME_SCREENS)
+def test_stall_watch_sees_the_2x_home_box_empty(name, monkeypatch):
+    src = stall_watch.HerdrSource("t", "opencode")
+    monkeypatch.setattr(src, "_herdr", lambda *args: _pane(name))
+    assert src.input_empty() is True
+
+
+def test_other_adapters_have_no_placeholder_pattern():
+    for agent in ("claude", "agy", "grok", "codex", "hermes"):
+        assert get_adapter(agent).input_placeholder_pattern is None, agent