feat(skills): add design-md skill for Google's DESIGN.md spec (#14876)

* 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.

* feat(skills): add design-md skill for Google's DESIGN.md spec

Built-in skill under skills/creative/ that teaches the agent to author,
lint, diff, and export DESIGN.md files — Google's open-source
(Apache-2.0) format for describing a visual identity to coding agents.

Covers:
- YAML front matter + markdown body anatomy
- Full token schema (colors, typography, rounded, spacing, components)
- Canonical section order + duplicate-heading rejection
- Component property whitelist + variants-as-siblings pattern
- CLI workflow via 'npx @google/design.md' (lint/diff/export/spec)
- Lint rule reference including WCAG contrast checks
- Common YAML pitfalls (quoted hex, negative dimensions, dotted refs)
- Starter template at templates/starter.md

Package verified live on npm (@google/design.md@0.1.1).

website/docs/user-guide/configuration.md

@@ -431,6 +431,35 @@ file_read_max_chars: 30000
 
 The agent also deduplicates file reads automatically — if the same file region is read twice and the file hasn't changed, a lightweight stub is returned instead of re-sending the content. This resets on context compression so the agent can re-read files after their content is summarized away.
 
+## Tool Output Truncation Limits
+
+Three related caps control how much raw output a tool can return before Hermes truncates it:
+
+```yaml
+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
+```
+
+- **`max_bytes`** — When a `terminal` command produces more than this many characters of combined stdout/stderr, Hermes keeps the first 40% and last 60% and inserts a `[OUTPUT TRUNCATED]` notice between them. Default `50000` (≈12-15K tokens across typical tokenisers).
+- **`max_lines`** — Upper bound on the `limit` parameter of a single `read_file` call. Requests above this are clamped so a single read can't flood the context window. Default `2000`.
+- **`max_line_length`** — Per-line cap applied when `read_file` emits the line-numbered view. Lines longer than this are truncated to this many chars followed by `... [truncated]`. Default `2000`.
+
+Raise the limits on models with large context windows that can afford more raw output per call. Lower them for small-context models to keep tool results compact:
+
+```yaml
+# Large context model (200K+)
+tool_output:
+  max_bytes: 150000
+  max_lines: 5000
+
+# Small local model (16K context)
+tool_output:
+  max_bytes: 20000
+  max_lines: 500
+```
+
 ## Git Worktree Isolation
 
 Enable isolated git worktrees for running multiple agents in parallel on the same repo: