feat(config): make tool output truncation limits configurable

Port from anomalyco/opencode#23770: expose a new `tool_output` config
section so users can tune the hardcoded truncation caps that apply to
terminal output and read_file pagination.

Three knobs under `tool_output`:
- max_bytes (default 50_000) — terminal stdout/stderr cap
- max_lines (default 2000) — read_file pagination cap
- max_line_length (default 2000) — per-line cap in line-numbered view

All three keep their existing hardcoded values as defaults, so behaviour
is unchanged when the section is absent. Power users on big-context
models can raise them; small-context local models can lower them.

Implementation:
- New `tools/tool_output_limits.py` reads the section with defensive
  fallback (missing/invalid values → defaults, never raises).
- `tools/terminal_tool.py` MAX_OUTPUT_CHARS now comes from
  get_max_bytes().
- `tools/file_operations.py` normalize_read_pagination() and
  _add_line_numbers() now pull the limits at call time.
- `hermes_cli/config.py` DEFAULT_CONFIG gains the `tool_output` section
  so `hermes setup` writes defaults into fresh configs.
- Docs page `user-guide/configuration.md` gains a "Tool Output
  Truncation Limits" section with large-context and small-context
  example configs.

Tests (18 new in tests/tools/test_tool_output_limits.py):
- Default resolution with missing / malformed / non-dict config.
- Full and partial user overrides.
- Coercion of bad values (None, negative, wrong type, str int).
- Shortcut accessors delegate correctly.
- DEFAULT_CONFIG exposes the section with the right defaults.
- Integration: normalize_read_pagination clamps to the configured
  max_lines.

hermes_cli/config.py

@@ -486,7 +486,27 @@ DEFAULT_CONFIG = {
     # exceed this are rejected with guidance to use offset+limit.
     # 100K chars ≈ 25–35K tokens across typical tokenisers.
     "file_read_max_chars": 100_000,
-    
+
+    # Tool-output truncation thresholds. When terminal output or a
+    # single read_file page exceeds these limits, Hermes truncates the
+    # payload sent to the model (keeping head + tail for terminal,
+    # enforcing pagination for read_file). Tuning these trades context
+    # footprint against how much raw output the model can see in one
+    # shot. Ported from anomalyco/opencode PR #23770.
+    #
+    # - max_bytes:       terminal_tool output cap, in chars
+    #                    (default 50_000 ≈ 12-15K tokens).
+    # - max_lines:       read_file pagination cap — the maximum `limit`
+    #                    a single read_file call can request before
+    #                    being clamped (default 2000).
+    # - max_line_length: per-line cap applied when read_file emits a
+    #                    line-numbered view (default 2000 chars).
+    "tool_output": {
+        "max_bytes": 50_000,
+        "max_lines": 2000,
+        "max_line_length": 2000,
+    },
+
     "compression": {
         "enabled": True,
         "threshold": 0.50,            # compress when context usage exceeds this ratio