feat(config): make tool output truncation limits configurable

[teknium1]

Summary

Port 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.

Motivation (from the upstream PR)

OpenCode had MAX_LINES = 2000 and MAX_BYTES = 50 * 1024 hardcoded in packages/opencode/src/tool/truncate.ts. Hermes-agent had the same constants hardcoded in two places:

• tools/terminal_tool.py — MAX_OUTPUT_CHARS = 50000 (terminal stdout cap)
• tools/file_operations.py — MAX_LINES = 2000 / MAX_LINE_LENGTH = 2000

Users on big-context models (opus-4.6, sonnet-4.6, MiniMax M2.7) wanted to let tools return more raw output before truncation. Users on small local models wanted the opposite.

Changes

tool_output:
  max_bytes: 50000        # terminal output cap (chars)
  max_lines: 2000         # read_file pagination cap
  max_line_length: 2000   # per-line cap in read_file's line-numbered view

• New tools/tool_output_limits.py — defensive reader. Missing/invalid values fall back to the pre-existing hardcoded defaults. Never raises.
• tools/terminal_tool.py — MAX_OUTPUT_CHARS now pulled via get_max_bytes() at call time.
• tools/file_operations.py — normalize_read_pagination() and _add_line_numbers() pull limits at call time.
• hermes_cli/config.py — DEFAULT_CONFIG gains the tool_output section so fresh installs write these keys.
• website/docs/user-guide/configuration.md — new section with large-context and small-context example configs.

Architectural differences from OpenCode

OpenCode's version routes all tool output through a Truncate.Service that also writes the full text to a scratch directory and returns a preview + hint. Hermes-agent's truncation lives at two separate call sites (terminal head/tail split, read_file pagination) so the port is a straight s/hardcoded/configurable swap rather than a service introduction. The config surface matches: tool_output.max_bytes / tool_output.max_lines use the same names as upstream. max_line_length is a Hermes-specific addition (OpenCode doesn't have an equivalent per-line cap).

Default-preserving by design: users who don't set the section get the identical behaviour they had before this PR.

Validation

	Before	After
Terminal cap	hardcoded 50000	tool_output.max_bytes (default 50000)
read_file cap	hardcoded 2000	tool_output.max_lines (default 2000)
Per-line cap	hardcoded 2000	tool_output.max_line_length (default 2000)
Behaviour w/o config	n/a	identical to before

• scripts/run_tests.sh tests/tools/test_tool_output_limits.py — 18/18 passing.
• scripts/run_tests.sh tests/tools/ -k 'file_op or read_file or pagination or terminal' — 237/237 passing.
• E2E: built a tmp HERMES_HOME with a config setting max_bytes: 200 / max_lines: 10, verified get_tool_output_limits() returns the overrides and normalize_read_pagination(limit=500) clamps to 10. Also verified the no-config path returns the defaults.

Credit

Ported from @anomaly's OpenCode (PR #23770 upstream).

[teknium1]

Closing as already on main. tools/tool_output_limits.py ships with get_max_bytes() / get_max_lines() / get_max_line_length(), wired into tools/terminal_tool.py (L2099-2103) and tools/file_operations.py (L487, L610). tool_output: section is in DEFAULT_CONFIG. All 18 tests in tests/tools/test_tool_output_limits.py pass on current main.

Credit to your OpenCode#23770 scout — the landed implementation matches the approach.