feat: add Codex CLI provider for subprocess integration (#80)

* feat: add Codex CLI provider for OpenAI subprocess integration

Add CodexCliProvider that wraps `codex exec --json` as a subprocess,
analogous to the existing ClaudeCliProvider pattern. This enables using
OpenAI's Codex CLI tool as a local LLM backend.

- CodexCliProvider: subprocess wrapper parsing JSONL event stream
- Credential reader for ~/.codex/auth.json with token expiry detection
- Factory integration: provider "codex-cli" and auth_method "codex-cli"
- Fix tilde expansion in workspace path for CLI providers
- 37 unit tests covering parsing, prompt building, credentials, and mocks

* fix: add tool call extraction to Codex CLI provider

- Extract shared tool call parsing into tool_call_extract.go
  (extractToolCallsFromText, stripToolCallsFromText, findMatchingBrace)
- Both ClaudeCliProvider and CodexCliProvider now share the same
  tool call extraction logic for PicoClaw-specific tools
- Fix cache token accounting: include cached_input_tokens in total
- Add 2 new tests for tool call extraction from JSONL events
- Update existing tests for corrected token calculations

* fix(docker): update Go version to match go.mod requirement

Dockerfile used golang:1.24-alpine but go.mod requires go >= 1.25.7.
This caused Docker builds to fail on all branches with:
  "go: go.mod requires go >= 1.25.7 (running go 1.24.13)"

Update to golang:1.25-alpine to match the project requirement.

* fix: handle codex CLI stderr noise without losing valid stdout

Codex writes diagnostic messages to stderr (e.g. rollout errors) which
cause non-zero exit codes even when valid JSONL output exists on stdout.
Parse stdout first before checking exit code to avoid false errors.

* style: fix gofmt formatting and update web search API in tests

- Remove trailing whitespace in web.go and base_test.go
- Update config_test.go and web_test.go for WebSearchToolOptions API

pkg/providers/http_provider.go

@@ -240,6 +240,9 @@ func CreateProvider(cfg *config.Config) (LLMProvider, error) {
 			}
 		case "openai", "gpt":
 			if cfg.Providers.OpenAI.APIKey != "" || cfg.Providers.OpenAI.AuthMethod != "" {
+				if cfg.Providers.OpenAI.AuthMethod == "codex-cli" {
+					return NewCodexProviderWithTokenSource("", "", CreateCodexCliTokenSource()), nil
+				}
 				if cfg.Providers.OpenAI.AuthMethod == "oauth" || cfg.Providers.OpenAI.AuthMethod == "token" {
 					return createCodexAuthProvider()
 				}
@@ -299,11 +302,17 @@ func CreateProvider(cfg *config.Config) (LLMProvider, error) {
 				}
 			}
 		case "claude-cli", "claudecode", "claude-code":
-			workspace := cfg.Agents.Defaults.Workspace
+			workspace := cfg.WorkspacePath()
 			if workspace == "" {
 				workspace = "."
 			}
 			return NewClaudeCliProvider(workspace), nil
+		case "codex-cli", "codex-code":
+			workspace := cfg.WorkspacePath()
+			if workspace == "" {
+				workspace = "."
+			}
+			return NewCodexCliProvider(workspace), nil
 		case "deepseek":
 			if cfg.Providers.DeepSeek.APIKey != "" {
 				apiKey = cfg.Providers.DeepSeek.APIKey