Step 22: Shell completion docs for bash, zsh, fish.

Cobra provides built-in sgard completion subcommand — no additional
code needed. README updated with installation instructions for each
shell.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

PROGRESS.md

@@ -7,7 +7,7 @@ ARCHITECTURE.md for design details.
 
 ## Current Status
 
-**Phase:** Phase 4 in progress. Step 21 complete, ready for Step 22.
+**Phase:** Phase 4 in progress. Steps 21–22 complete, ready for Step 23.
 
 **Last updated:** 2026-03-24
 
@@ -42,7 +42,7 @@ ARCHITECTURE.md for design details.
 
 ## Up Next
 
-Step 22: Shell Completion.
+Step 23: TLS Transport for sgardd.
 
 ## Known Issues / Decisions Deferred
 
@@ -85,3 +85,4 @@ Step 22: Shell Completion.
 | 2026-03-24 | — | Locked files + dir-only entries. v2.0.0 released. |
 | 2026-03-24 | — | Phase 4 planned (Steps 21–27): lock/unlock, shell completion, TLS, DEK rotation, real FIDO2, test cleanup. |
 | 2026-03-24 | 21 | Lock/unlock toggle commands. garden/lock.go, cmd/sgard/lock.go, 6 tests. |
+| 2026-03-24 | 22 | Shell completion: cobra built-in, README docs for bash/zsh/fish. |

PROJECT_PLAN.md

@@ -232,8 +232,8 @@ Depends on Steps 17, 18.
 
 ### Step 22: Shell Completion
 
-- [ ] `cmd/sgard/completion.go`: cobra's built-in completion for bash, zsh, fish
+- [x] Cobra provides built-in `sgard completion` for bash, zsh, fish, powershell — no code needed
-- [ ] Update README with completion installation instructions
+- [x] README updated with shell completion installation instructions
 
 ### Step 23: TLS Transport for sgardd
 

README.md

@@ -41,6 +41,21 @@ in your packages.
 Binaries are also available on the
 [releases page](https://github.com/kisom/sgard/releases).
 
+### Shell completion
+
+```sh
+# Bash (add to ~/.bashrc)
+source <(sgard completion bash)
+
+# Zsh (add to ~/.zshrc)
+source <(sgard completion zsh)
+
+# Fish
+sgard completion fish | source
+# To load on startup:
+sgard completion fish > ~/.config/fish/completions/sgard.fish
+```
+
 ## Quick start
 
 ```sh