docs: add reverse mode documentation with examples

- Add --reverse flag to tree command documentation
- Document normal vs reverse mode differences
- Add comprehensive reverse mode section with use cases
- Update examples to show both directions

commands/dep.md

@@ -21,6 +21,11 @@ Manage dependencies between beads issues.
 - **tree**: Show dependency tree for an issue
   - $1: "tree"
   - $2: Issue ID
+  - Flags:
+    - `--reverse`: Show dependent tree (what was discovered from this) instead of dependency tree (what blocks this)
+    - `--json`: Output as JSON
+    - `--max-depth N`: Limit tree depth (default: 50)
+    - `--show-all-paths`: Show all paths (no deduplication for diamond dependencies)
 
 - **cycles**: Detect dependency cycles
 
@@ -34,5 +39,29 @@ Manage dependencies between beads issues.
 ## Examples
 
 - `bd dep add bd-10 bd-20 --type blocks`: bd-10 blocks bd-20
-- `bd dep tree bd-20`: Show what blocks bd-20 and what bd-20 blocks
+- `bd dep tree bd-20`: Show what blocks bd-20 (dependency tree going UP)
+- `bd dep tree bd-1 --reverse`: Show what was discovered from bd-1 (dependent tree going DOWN)
+- `bd dep tree bd-1 --reverse --max-depth 3`: Show discovery tree with depth limit
 - `bd dep cycles`: Check for circular dependencies
+
+## Reverse Mode: Discovery Trees
+
+The `--reverse` flag inverts the tree direction to show **dependents** instead of **dependencies**:
+
+**Normal mode** (`bd dep tree ISSUE`):
+- Shows what blocks you (dependency tree)
+- Answers: "What must I complete before I can work on this?"
+- Tree flows **UP** toward prerequisites
+
+**Reverse mode** (`bd dep tree ISSUE --reverse`):
+- Shows what was discovered from you (dependent tree)
+- Answers: "What work was discovered while working on this?"
+- Tree flows **DOWN** from goal to discovered tasks
+- Perfect for visualizing work breakdown and discovery chains
+
+**Use Cases:**
+- Document project evolution and how work expanded from initial goal
+- Share "how we got here" context with stakeholders
+- Visualize work breakdown structure from epics
+- Track discovery chains (what led to what)
+- Show yak shaving journeys in retrospectives