Adds a `load_skill` tool that takes a skill id and returns the
SKILL.md body plus the sibling companion-file list in one tool
call. The existing progressive-disclosure pattern (system prompt
lists skills → model `read_file <path>`) still works; this tool
is the higher-level affordance for skills that ship with multiple
resource files.
Implementation:
* `LoadSkillTool` lives in `crates/tui/src/tools/skill.rs`. Read-
only, auto-approved, parallel-safe.
* On call, resolves the active skills directory via the new
`skills::resolve_skills_dir` helper, which mirrors
`App::new`'s hierarchy: `<workspace>/.agents/skills` →
`<workspace>/skills` → `~/.deepseek/skills`. No new plumbing
through ToolContext — the workspace is already there.
* Returns the skill body wrapped in a self-contained block:
description quote, source path, the SKILL.md verbatim, and a
`## Companion files` section listing siblings (sorted lex,
deterministic for tests). Solo skills skip the companions
section entirely so the tool result stays tight.
* Errors with a helpful hint when the name is unknown — the
hint includes the catalogue ("Available: foo, bar, baz") so
the model can recover without an extra discovery call.
* Wired into `ToolRegistryBuilder::with_skill_tools` and pulled
into both Agent and Plan tool-setup paths. Plan mode benefits
because skills are read-only references that planners often
need.
Tests:
5 unit tests covering: description-headed body, companion
enumeration excluding SKILL.md and nested dirs, empty result
for solo skills, and the conditional `## Companion files`
section.
Hunter Bown
e8af3cd37d