feat: rename pass_mgr → secret-mgr, add ego-mgr binary and skill

M1: Rename pass_mgr to secret-mgr
- Rename directory, binary, and Go module
- Update install.mjs to build/install secret-mgr
- Update pcexec.ts to support secret-mgr patterns (with legacy pass_mgr compat)
- Update plugin config schema (passMgrPath → secretMgrPath)
- Create new skills/secret-mgr/SKILL.md
- install.mjs now initializes ego.json on install

M2: Implement ego-mgr binary (Go)
- Agent Scope and Public Scope column management
- Commands: add column/public-column, delete, set, get, show, list columns
- pcexec environment validation (AGENT_VERIFY, AGENT_ID, AGENT_WORKSPACE)
- File locking for concurrent write safety
- Proper exit codes per spec (0-6)
- Agent auto-registration on read/write
- Global column name uniqueness enforcement

M3: ego-mgr Skill
- Create skills/ego-mgr/SKILL.md with usage guide and examples

Ref: REQUIREMENTS_EGO_MGR.md

skills/ego-mgr/SKILL.md

@@ -0,0 +1,105 @@
+---
+name: ego-mgr
+description: Manage agent personal information (name, email, timezone, etc.). Use when storing, retrieving, listing, or managing agent profile fields. Trigger on requests about agent identity, personal info, profile settings, or ego-mgr usage. MUST call ego-mgr via the pcexec tool.
+---
+
+# Ego Manager
+
+## Purpose
+Use ego-mgr to manage agent personal information fields. Supports per-agent fields (Agent Scope) and shared fields (Public Scope).
+
+## Mandatory safety rule
+Always invoke ego-mgr through the `pcexec` tool. Do NOT run ego-mgr directly.
+
+## Concepts
+
+- **Agent Scope columns**: Each agent stores its own value independently
+- **Public Scope columns**: All agents share the same value
+- Column names are globally unique — a name cannot be both agent-scope and public-scope
+
+## Workflow
+
+1. First, create a column: `ego-mgr add column <name>` or `ego-mgr add public-column <name>`
+2. Then, set its value: `ego-mgr set <name> <value>`
+3. Read it: `ego-mgr get <name>` or `ego-mgr show`
+
+## Commands (run via pcexec)
+
+### Add columns
+```bash
+# Agent-scope column (per-agent values)
+ego-mgr add column <column-name> [--default <default-value>]
+
+# Public-scope column (shared by all agents)
+ego-mgr add public-column <column-name> [--default <default-value>]
+```
+
+### Delete a column
+```bash
+ego-mgr delete <column-name>
+```
+Removes the column and all its values across all scopes.
+
+### Set a value
+```bash
+ego-mgr set <column-name> <value>
+```
+Automatically writes to the correct scope (agent or public) based on column type.
+
+### Get a value
+```bash
+ego-mgr get <column-name>
+```
+Outputs just the value (no label).
+
+### Show all fields
+```bash
+ego-mgr show
+```
+Lists all fields with values (public first, then agent-scope).
+
+### List column names
+```bash
+ego-mgr list columns
+```
+Lists all column names (public first, then agent-scope).
+
+## Error exit codes
+
+| Code | Meaning |
+|------|---------|
+| 0 | Success |
+| 1 | Usage error |
+| 2 | Column not found |
+| 3 | Column already exists |
+| 4 | Permission error (not via pcexec) |
+| 5 | File lock failed |
+| 6 | JSON read/write error |
+
+## Common use cases
+
+### Set up agent identity
+```bash
+ego-mgr add column name
+ego-mgr set name "小智"
+ego-mgr add column email
+ego-mgr set email "zhi@example.com"
+```
+
+### Set shared config
+```bash
+ego-mgr add public-column timezone --default UTC
+ego-mgr add public-column language --default zh-CN
+```
+
+### Check current profile
+```bash
+ego-mgr show
+```
+
+## Usage notes
+
+- Always create columns before setting values
+- Column names are case-sensitive
+- Public scope values are readable and writable by all agents
+- Agent scope values are isolated per-agent