refactor: centralize environment variable key constants

[dev-miro26]

Closes: #1638

📝 Description

Environment variable names for runtime configuration (e.g. PICOCLAW_HOME,
PICOCLAW_CONFIG, PICOCLAW_BUILTIN_SKILLS, PICOCLAW_BINARY) were
duplicated as inline string literals across 11 files. A single typo in any
one of them would silently read the wrong variable with no compiler warning.
This PR replaces every inline occurrence with a named exported constant,
making all supported runtime knobs discoverable in one place and preventing
future typos.
Summary of changes:

• Add pkg/config/envkeys.go with four exported constants (EnvHome,
  EnvConfig, EnvBuiltinSkills, EnvBinary)
• Export credential.SSHKeyPathEnvVar (was the unexported sshKeyEnv);
  add picoclawHome package-local constant to avoid a circular import
• Add openclaw.OpenclawHomeEnvVar and providers.CodexHomeEnvVar in
  their respective domain packages
• Replace all os.Getenv("PICOCLAW_*") call sites with the new constants
  across 9 files

🗣️ Type of Change

• ⚡ Code refactoring (no functional changes, no api changes)

🤖 AI Code Generation

• 🤖 Fully AI-generated (100% AI, 0% Human)

🔗 Related Issue

📚 Technical Context (Skip for Docs)

• Reference URL: N/A
• Reasoning: Centralizing string constants is the standard Go idiom
  for preventing typos and improving discoverability. The existing
  credential.PassphraseEnvVar was already following this pattern;
  this PR extends it consistently to all picoclaw-specific runtime keys.

🧪 Test Environment

• Hardware: PC (development machine)
• OS: Ubuntu 24.04
• Model/Provider: N/A (refactor only)
• Channels: N/A (refactor only)

☑️ Checklist

• My code/docs follow the style of this project.
• I have performed a self-review of my own changes.
• I have updated the documentation accordingly.

[CLAassistant]

All committers have signed the CLA.

[dev-miro26]

Hi, @alexhoshina
Could you review my first PR?
Please leave your feedback kindly.
Thank you.

[alexhoshina]

hi @dev-miro26, please check the ci~

[yinwm]

Review Summary

Thanks for this refactoring PR! The intent is great — centralizing environment variable keys is a good practice to prevent typos and improve discoverability.

However, I found several issues that need to be addressed before merging.

---

🚨 Critical: Syntax Error (blocking CI)

File: pkg/migrate/sources/openclaw/openclaw_handler.go:6-8

In Go, import statements must appear before any other declarations. You placed a const before import:

package openclaw

const OpenclawHomeEnvVar = "OPENCLAW_HOME"  // ❌ Wrong position

import (  // ❌ Syntax error: imports must appear before other declarations
    ...
)

Fix: Move the const after the import block:

package openclaw

import (
    "fmt"
    ...
)

const OpenclawHomeEnvVar = "OPENCLAW_HOME"

This is causing all CI checks to fail (Linter, Security Check, Tests).

---

⚠️ Missing Replacement

File: web/backend/api/gateway.go:390

This line still uses the hardcoded string:

cmd.Env = append(cmd.Env, "PICOCLAW_CONFIG="+h.configPath)

Should be changed to:

cmd.Env = append(cmd.Env, config.EnvConfig+"="+h.configPath)

(Don't forget to add the import for github.com/sipeed/picoclaw/pkg/config if not already present)

---

💡 Suggestion: Add PICOCLAW_GATEWAY_HOST

The PICOCLAW_GATEWAY_HOST environment variable is used in:

• pkg/config/config.go:628 (struct tag)
• web/backend/api/gateway.go:393 (string concatenation)

Consider adding it to pkg/config/envkeys.go for completeness:

// EnvGatewayHost overrides the host address for the gateway server.
// Default: "127.0.0.1"
EnvGatewayHost = "PICOCLAW_GATEWAY_HOST"

---

📋 Checklist Before Merge

• Fix the syntax error in openclaw_handler.go (move const after import)
• Replace hardcoded string in gateway.go:390
• Sign the CLA (currently pending) — visit: https://cla-assistant.io/sipeed/picoclaw?pullRequest=1730
• Ensure all CI checks pass (Linter, Security Check, Tests)

---

✅ What's Done Well

• pkg/config/envkeys.go is well-documented with clear comments
• Handling of circular import in credential.go is pragmatic
• Non-picoclaw env vars (OPENCLAW_HOME, CODEX_HOME) placed in their domain packages — good DDD

Once the issues above are fixed, this will be a solid refactoring PR! 🦞

[dev-miro26]

Hi, @alexhoshina @yinwm
Please review this PR again.

[yinwm]

Code Review: PR #1730

✅ Strengths

1. Correct refactoring approach - Centralizing environment variable constants is a standard Go best practice
2. Clear documentation - Comments in pkg/config/envkeys.go are well-written, explaining each constant's purpose and default value
3. Precise scope - Pure refactoring with no functional changes
4. Consistent style - Follows the existing pattern established by credential.PassphraseEnvVar

---

⚠️ Points to Consider

1. Circular Import Technical Debt

pkg/credential/credential.go:26-29:

// picoclawHome is a package-local copy of config.EnvHome. It is kept here to
// avoid a circular import between pkg/credential and pkg/config.
const picoclawHome = "PICOCLAW_HOME"

Issue: Duplicating the constant value creates potential for inconsistency. If someone updates config.EnvHome but forgets to sync this local copy, it would cause subtle bugs.

Suggestion: Consider placing these constants in a more foundational package (e.g., internal/envkeys or pkg/constants) that both config and credential can depend on without circular imports.

---

2. Missing Unit Tests (Minor)

While this is a pure refactor, it would be nice to have a simple test to verify constant values:

func TestEnvKeysMatchExpected(t *testing.T) {
    tests := []struct {
        constant, expected string
    }{
        {EnvHome, "PICOCLAW_HOME"},
        {EnvConfig, "PICOCLAW_CONFIG"},
        {EnvBuiltinSkills, "PICOCLAW_BUILTIN_SKILLS"},
        {EnvBinary, "PICOCLAW_BINARY"},
        {EnvGatewayHost, "PICOCLAW_GATEWAY_HOST"},
    }
    for _, tt := range tests {
        if tt.constant != tt.expected {
            t.Errorf("got %q, want %q", tt.constant, tt.expected)
        }
    }
}

---

📋 Summary

Item	Status
Code Quality	✅ Good
Test Coverage	⚠️ Missing (acceptable for pure refactor)
Documentation	✅ Clear
Risk	🟢 Very Low

Recommendation: Approve for merge. Consider addressing the circular import debt in a follow-up PR.

🤖 Generated with Claude Code

[Orgmar]

@dev-miro26 Nice cleanup! Replacing scattered inline env var strings with centralized constants across 11 files is exactly the kind of refactor that prevents silent bugs down the road. Follows the existing pattern from credential.PassphraseEnvVar too, so it feels consistent.

We're running a PicoClaw Dev Group on Discord for contributors to connect. If you're interested, email support@sipeed.com with subject [Join PicoClaw Dev Group] dev-miro26 and we'll send you the invite link!