Add CI and lint GitHub Actions workflows

[alishakawaguchi]

Summary

• Add CI workflow (ci.yml): unit tests with race detector + build verification on PRs and pushes to main
• Add lint workflow (lint.yml): gofmt formatting check + golangci-lint v2 with inline PR annotations (per-module)
• Add .golangci.yaml: curated linter set adapted from devenv/cli with appropriate exclusions for CLI tools and e2e test infra
• Add .gitignore: ignore .entire/ runtime data and built binaries
• Fix existing lint issues: unused types, unchecked json.Marshal errors, formatting alignment, dead code removal

Test plan

• gofmt -l . returns empty (all files formatted)
• golangci-lint run ./... passes in agents/entire-agent-kiro (0 issues)
• golangci-lint run ./... passes in e2e (0 issues)
• go test -race -count=1 ./... passes in agents/entire-agent-kiro (2/2 packages)
• go build -o /dev/null ./cmd/entire-agent-kiro succeeds

🤖 Generated with Claude Code

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Note

Low Risk
Low risk: mostly adds GitHub Actions workflows and lint configuration; code changes are small, lint-driven cleanup (error handling and dead code removal) with minimal behavior impact.

Overview
Adds GitHub Actions automation: a CI workflow to run go test -race and a build check for agents/entire-agent-kiro, plus a Lint workflow that enforces gofmt and runs golangci-lint for both agents/entire-agent-kiro and e2e.

Introduces a repo-wide .golangci.yaml and updates .gitignore to exclude .entire/ runtime data and the built entire-agent-kiro binary. To satisfy the new linting, it also tightens error handling around json.Marshal, removes unused execution-index types, and makes minor cleanup/refactors (e.g., stubSessionID constant reuse and simpler session file path building).

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