feat: /gsd:fast command for trivial inline tasks (#609)

New lightweight command for tasks too small to justify planning overhead:
typo fixes, config changes, forgotten commits, simple additions.

- Runs inline in current context (no subagent spawn)
- No PLAN.md or SUMMARY.md generated
- Scope guard: redirects to /gsd:quick if task needs >3 file edits
- Atomic commit with conventional commit format
- Logs to STATE.md quick tasks table if present

Complements /gsd:quick (which spawns planner+executor) for cases where
the planning overhead exceeds the actual work.

Closes #609

commands/gsd/fast.md

@@ -0,0 +1,30 @@
+---
+name: gsd:fast
+description: Execute a trivial task inline — no subagents, no planning overhead
+argument-hint: "[task description]"
+allowed-tools:
+  - Read
+  - Write
+  - Edit
+  - Bash
+  - Grep
+  - Glob
+---
+
+<objective>
+Execute a trivial task directly in the current context without spawning subagents
+or generating PLAN.md files. For tasks too small to justify planning overhead:
+typo fixes, config changes, small refactors, forgotten commits, simple additions.
+
+This is NOT a replacement for /gsd:quick — use /gsd:quick for anything that
+needs research, multi-step planning, or verification. /gsd:fast is for tasks
+you could describe in one sentence and execute in under 2 minutes.
+</objective>
+
+<execution_context>
+@~/.claude/get-shit-done/workflows/fast.md
+</execution_context>
+
+<process>
+Execute the fast workflow from @~/.claude/get-shit-done/workflows/fast.md end-to-end.
+</process>