feat: add /gsd-edit-phase command to modify roadmap phases in place (#2753)

Adds a new slash command that lets developers modify any field of an
existing phase in ROADMAP.md without affecting phase number or position.

- commands/gsd/edit-phase.md: command file with --force flag support
- get-shit-done/workflows/edit-phase.md: full workflow with status guard,
  depends_on validation, diff+confirmation, and STATE.md update
- tests/edit-phase.test.cjs: 32 tests covering all acceptance criteria
- docs/INVENTORY.md, INVENTORY-MANIFEST.json, COMMANDS.md: registered

Closes #2617

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/COMMANDS.md

@@ -425,6 +425,28 @@ Append new phase to roadmap.
 /gsd-add-phase                      # Interactive — describe the phase
 ```
 
+### `/gsd-edit-phase`
+
+Edit any field of an existing roadmap phase in place.
+
+| Argument | Required | Description |
+|----------|----------|-------------|
+| `N` | Yes | Phase number to edit |
+
+| Flag | Description |
+|------|-------------|
+| `--force` | Allow editing in-progress or completed phases |
+
+**Prerequisites:** `.planning/ROADMAP.md` exists, phase N must exist
+**Produces:** Updated phase section in ROADMAP.md (in place, number and position preserved)
+
+```bash
+/gsd-edit-phase 5                   # Edit any field of phase 5 (future phases only)
+/gsd-edit-phase 5 --force           # Edit phase 5 even if in-progress or completed
+```
+
+---
+
 ### `/gsd-insert-phase`
 
 Insert urgent work between phases using decimal numbering.

docs/INVENTORY-MANIFEST.json

@@ -56,6 +56,7 @@
       "/gsd-discuss-phase",
       "/gsd-do",
       "/gsd-docs-update",
+      "/gsd-edit-phase",
       "/gsd-eval-review",
       "/gsd-execute-phase",
       "/gsd-explore",
@@ -145,6 +146,7 @@
       "discuss-phase.md",
       "do.md",
       "docs-update.md",
+      "edit-phase.md",
       "eval-review.md",
       "execute-phase.md",
       "execute-plan.md",

docs/INVENTORY.md

@@ -54,7 +54,7 @@ Full roster at `agents/gsd-*.md`. The "Primary doc" column flags whether [`docs/
 
 ---
 
-## Commands (85 shipped)
+## Commands (86 shipped)
 
 Full roster at `commands/gsd/*.md`. The groupings below mirror `docs/COMMANDS.md` section order; each row carries the command name, a one-line role derived from the command's frontmatter `description:`, and a link to the source file. `tests/command-count-sync.test.cjs` locks the count against the filesystem.
 
@@ -92,6 +92,7 @@ Full roster at `commands/gsd/*.md`. The groupings below mirror `docs/COMMANDS.md
 | Command | Role | Source |
 |---------|------|--------|
 | `/gsd-add-phase` | Add phase to end of current milestone in roadmap. | [commands/gsd/add-phase.md](../commands/gsd/add-phase.md) |
+| `/gsd-edit-phase` | Edit any field of an existing roadmap phase in place, preserving number and position. | [commands/gsd/edit-phase.md](../commands/gsd/edit-phase.md) |
 | `/gsd-insert-phase` | Insert urgent work as decimal phase (e.g., 72.1) between existing phases. | [commands/gsd/insert-phase.md](../commands/gsd/insert-phase.md) |
 | `/gsd-remove-phase` | Remove a future phase from roadmap and renumber subsequent phases. | [commands/gsd/remove-phase.md](../commands/gsd/remove-phase.md) |
 | `/gsd-add-tests` | Generate tests for a completed phase based on UAT criteria and implementation. | [commands/gsd/add-tests.md](../commands/gsd/add-tests.md) |
@@ -175,7 +176,7 @@ Full roster at `commands/gsd/*.md`. The groupings below mirror `docs/COMMANDS.md
 
 ---
 
-## Workflows (83 shipped)
+## Workflows (84 shipped)
 
 Full roster at `get-shit-done/workflows/*.md`. Workflows are thin orchestrators that commands reference internally; most are not read directly by end users. Rows below map each workflow file to its role (derived from the `<purpose>` block) and, where applicable, to the command that invokes it.
 
@@ -202,6 +203,7 @@ Full roster at `get-shit-done/workflows/*.md`. Workflows are thin orchestrators
 | `discuss-phase.md` | Extract implementation decisions through iterative gray-area discussion. | `/gsd-discuss-phase` |
 | `do.md` | Route freeform text from the user to the best matching GSD command. | `/gsd-do` |
 | `docs-update.md` | Generate, update, and verify canonical and hand-written project documentation. | `/gsd-docs-update` |
+| `edit-phase.md` | Edit any field of an existing phase in ROADMAP.md in place, preserving number and position. | `/gsd-edit-phase` |
 | `eval-review.md` | Retroactive audit of an implemented AI phase's evaluation coverage. | `/gsd-eval-review` |
 | `execute-phase.md` | Execute all plans in a phase using wave-based parallel execution. | `/gsd-execute-phase` |
 | `execute-plan.md` | Execute a phase prompt (PLAN.md) and create the outcome summary (SUMMARY.md). | `execute-phase.md` (per-plan subagent) |