feat: add /ego-mgr slash command and rename pcexec to pc-exec

Changes:
1. Add /ego-mgr slash command with subcommands:
   - get, set, list, delete, add-column, add-public-column, show
   - Uses pcExec to call ego-mgr binary with proper env vars

2. Rename pcexec → pc-exec throughout codebase:
   - Tool name: pcexec → pc-exec
   - Function exports: pcexec → pcExec, pcexecSync → pcExecSync
   - Updated all references in skills and plugin files

3. Translate all Chinese text to English:
   - ego-mgr-slash.ts responses
   - slash-commands.ts responses
   - SKILL.md files remain in English

skills/secret-mgr/SKILL.md

@@ -1,6 +1,6 @@
 ---
 name: secret-mgr
-description: Manage OpenClaw agent credentials (usernames/secrets). Use when storing, retrieving, listing, generating, or removing credentials for an agent. Trigger on requests about saving or fetching usernames, passwords, tokens, API keys, or other secrets. MUST call secret-mgr via the pcexec tool.
+description: Manage OpenClaw agent credentials (usernames/secrets). Use when storing, retrieving, listing, generating, or removing credentials for an agent. Trigger on requests about saving or fetching usernames, passwords, tokens, API keys, or other secrets. MUST call secret-mgr via the pc-exec tool.
 ---
 
 # Secret Manager
@@ -9,9 +9,9 @@ description: Manage OpenClaw agent credentials (usernames/secrets). Use when sto
 Use secret-mgr to store and retrieve agent-scoped credentials (username/secret pairs) and generate secrets.
 
 ## Mandatory safety rule
-Always invoke secret-mgr through the `pcexec` tool. Do NOT run secret-mgr directly.
+Always invoke secret-mgr through the `pc-exec` tool. Do NOT run secret-mgr directly.
 
-## Commands (run via pcexec)
+## Commands (run via pc-exec)
 
 - List keys for current agent
   - `secret-mgr list`
@@ -50,19 +50,19 @@ Always invoke secret-mgr through the `pcexec` tool. Do NOT run secret-mgr direct
 - Storing can be explicit (user asks) or proactive after the agent successfully registers/creates an account.
 - Secrets should be fetched and used immediately in a command, not displayed (e.g., `xxx_cli login --user $(secret-mgr get-username --key some_key) --pass $(secret-mgr get-secret --key some_key)`).
 
-## Examples (pcexec)
+## Examples (pc-exec)
 
 - Store credentials
-  - pcexec: `secret-mgr set --key github --username alice --secret <secret>`
+  - pc-exec: `secret-mgr set --key github --username alice --secret <secret>`
 
 - Retrieve username
-  - pcexec: `secret-mgr get-username --key github`
+  - pc-exec: `secret-mgr get-username --key github`
 
 - Retrieve secret
-  - pcexec: `secret-mgr get-secret --key github`
+  - pc-exec: `secret-mgr get-secret --key github`
 
 - Generate secret
-  - pcexec: `secret-mgr generate --key github`
+  - pc-exec: `secret-mgr generate --key github`
 
 - Delete entry
-  - pcexec: `secret-mgr unset --key github`
+  - pc-exec: `secret-mgr unset --key github`