feat(hawk-sdk-go): production hardening

[Patel230]

Summary

Production-hardening pass for hawk-sdk-go that brings the repo to top-50
OSS repository standards. The branch contains two commits — a code-quality
pass and a re-baseline + full-OSS-bootstrap pass — both targeting main
(this repo does not have a dev branch).

This SDK had no README, LICENSE, CHANGELOG, CONTRIBUTING, SECURITY,
CODE_OF_CONDUCT, .gitignore, .gitattributes, or .github/ directory at all
— it was a brand-new module without any of the standard OSS scaffolding.
This PR lands the full bootstrap and aligns the SDK version with the rest of
the hawk-eco ecosystem (hawk, tok, eyrie, yaad, trace, sight,
inspect).

The mandate (per GOAL.md) is that this SDK be the reference Go SDK for
hawk daemon clients, comparable in quality to openai-go,
anthropic-sdk-go, langchaingo, sashabaranov/go-openai.

Commits

1. feat(hawk-sdk-go): production hardening — linter, errcheck, infrastructure
2. feat(hawk-sdk-go): re-baseline to v0.2.0, add Version + User-Agent, full OSS bootstrap

---

What's in commit 1 — code-quality pass

• .golangci.yml — strict v2 config: errcheck, staticcheck,
  gocritic (diagnostic + performance), unused, ineffassign,
  misspell, noctx, bodyclose, unconvert, whitespace.
• All errcheck issues fixed — every resp.Body.Close() is
  deferred-and-discarded explicitly.
• Makefile with standard targets.
• .editorconfig.

---

What's in commit 2 — version + User-Agent + full OSS bootstrap

Version 0.2.0 — new surface

File	Change
version.go (NEW)	const Version = "0.2.0" + userAgent() helper
client.go	every outbound HTTP request now sets User-Agent: hawk-sdk-go/0.2.0 (8 sites: Health, Chat, ChatStream, Sessions, Session, Messages, DeleteSession, Stats)
client_test.go	daemon-version mock fixture 0.3.0 → 0.2.0 (cosmetic — the test does not assert on this value)

The User-Agent pattern matches eyrie's client/client.go so a single
ecosystem-wide convention applies.

New OSS bootstrap (every one of these was missing)

File	Purpose
LICENSE	MIT
README.md	install, usage (Health / Chat / ChatStream / custom base URL / typed errors), full API surface, versioning, semver guarantees
CHANGELOG.md	Keep-a-Changelog format with [Unreleased] for this PR + a backfilled [0.0.1] entry for the two prior commits
CONTRIBUTING.md	quick start, branch flow (this repo branches from main), conventional commits, code standards (incl. the User-Agent rule), testing, version-bump procedure
SECURITY.md	vulnerability reporting via GitHub Security Advisories, in-scope examples (token leakage, TLS misuse, redirect host escape), out-of-scope pointers (daemon issues → hawk repo)
CODE_OF_CONDUCT.md	Contributor Covenant 2.1
.gitignore	Go test artifacts, IDE, OS, build caches, go.work
.gitattributes	LF normalization, binary detection, linguist hint to collapse go.sum
.github/workflows/ci.yml	race tests + coverage upload, golangci-lint v2, govulncheck, multi-platform build matrix (linux/darwin/windows × amd64/arm64)
.github/dependabot.yml	weekly gomod + github-actions
.github/PULL_REQUEST_TEMPLATE.md	Summary / Changes / API impact (with version-bump reminder) / Daemon compatibility (asks which daemon SHA was tested against) / Testing / Checklist
.github/ISSUE_TEMPLATE/bug_report.yml	surface dropdown (Client / ChatStream / Retry / Errors / Agent-Tool-Workflow / Build), required SDK + daemon + Go versions
.github/ISSUE_TEMPLATE/feature_request.yml	kind selector + solo-dev fit checks incl. "does not break wire-compatibility with existing daemon versions"
.github/ISSUE_TEMPLATE/config.yml	routes security to advisories, questions to discussions, blocks blank issues

Cleanup

• gofmt -w on client.go and retry.go to remove trailing-blank-line
  drift from commit 1.

Verification

Check	Status
go build ./...	✅ clean
go vet ./...	✅ clean
go test -race -count=1 -timeout=60s ./...	✅ pass
gofmt -l .	✅ empty (whole module is gofmt-clean)

Test plan

• make build
• make test with -race
• go vet ./...
• gofmt -l . empty
• CI on this PR will run lint, security scan (govulncheck),
  tests, and the multi-platform build matrix