chore: prepare clipx for public release

[karngyan]

Summary

Prepares clipx for public release / announcement.

Changes

• Doc comments: Added package-level docs and improved godoc for all exported types and functions
• Homebrew support: Added brews section to goreleaser config — on release, a formula is auto-published to gomantics/homebrew-tap so users can brew install gomantics/tap/clipx
• README polish:
  • Added CI, Go Report Card, License, and Release badges
  • Added Homebrew as the recommended install method
  • Added download binary section pointing to releases page
  • Fixed protocol docs (chunk size is 1300 bytes, not 16KB)
  • Added Contributing section
• CONTRIBUTING.md: Development guide with project structure, build instructions, and contribution workflow
• Release footer: Updated goreleaser release notes to include brew install instructions

Homebrew tap setup

Created gomantics/homebrew-tap repo. When the next release is cut via the Release workflow, goreleaser will automatically push the formula there. Users will be able to install via:

brew install gomantics/tap/clipx

Checklist

• Tests pass (go test -race ./...)
• go vet clean
• homebrew-tap repo created
• No breaking changes

[github-actions]

📊 Code Coverage Report

total:							(statements)		26.8%

Coverage by file

github.com/gomantics/clipx/clipx/clipboard.go:49:	Read			0.0%
github.com/gomantics/clipx/clipx/clipboard.go:55:	Write			0.0%
github.com/gomantics/clipx/clipx/config.go:16:		ConfigPath		100.0%
github.com/gomantics/clipx/clipx/config.go:22:		LoadConfig		77.8%
github.com/gomantics/clipx/clipx/config.go:38:		SaveConfig		71.4%
github.com/gomantics/clipx/clipx/net.go:15:		ResolveAddr		88.9%
github.com/gomantics/clipx/clipx/net.go:35:		PingPeer		0.0%
github.com/gomantics/clipx/clipx/node.go:52:		NewNode			0.0%
github.com/gomantics/clipx/clipx/node.go:57:		NewNodeWithClipboard	0.0%
github.com/gomantics/clipx/clipx/node.go:90:		Start			0.0%
github.com/gomantics/clipx/clipx/node.go:99:		Stop			0.0%
github.com/gomantics/clipx/clipx/node.go:108:		connectPeer		0.0%
github.com/gomantics/clipx/clipx/node.go:119:		sendToPeer		0.0%
github.com/gomantics/clipx/clipx/node.go:147:		listen			83.3%
github.com/gomantics/clipx/clipx/node.go:197:		handleClip		75.0%
github.com/gomantics/clipx/clipx/node.go:205:		handleChunk		81.5%
github.com/gomantics/clipx/clipx/node.go:256:		applyClipboard		85.7%
github.com/gomantics/clipx/clipx/node.go:280:		watchClipboard		0.0%
github.com/gomantics/clipx/clipx/node.go:325:		sendToAllPeers		0.0%
github.com/gomantics/clipx/clipx/node.go:376:		maintenance		0.0%
github.com/gomantics/clipx/clipx/node.go:409:		clipPreview		100.0%
github.com/gomantics/clipx/clipx/node.go:418:		isTimeout		0.0%
github.com/gomantics/clipx/clipx/node.go:425:		isConnectionError	0.0%
github.com/gomantics/clipx/clipx/protocol.go:47:	encodeMessage		100.0%
github.com/gomantics/clipx/clipx/protocol.go:58:	decodeMessage		100.0%
github.com/gomantics/clipx/clipx/protocol.go:72:	encodeClipPayload	100.0%
github.com/gomantics/clipx/clipx/protocol.go:81:	decodeClipPayload	100.0%
github.com/gomantics/clipx/clipx/protocol.go:89:	encodeChunkPayload	100.0%
github.com/gomantics/clipx/clipx/protocol.go:99:	decodeChunkPayload	100.0%
github.com/gomantics/clipx/clipx/protocol.go:111:	HashContent		100.0%
github.com/gomantics/clipx/cmd/clipx/main.go:21:	getVersion		0.0%
github.com/gomantics/clipx/cmd/clipx/main.go:31:	main			0.0%
github.com/gomantics/clipx/cmd/clipx/main.go:75:	printUsage		0.0%
github.com/gomantics/clipx/cmd/clipx/main.go:100:	cmdRun			0.0%
github.com/gomantics/clipx/cmd/clipx/main.go:133:	cmdPair			0.0%
github.com/gomantics/clipx/cmd/clipx/main.go:162:	cmdUnpair		0.0%
github.com/gomantics/clipx/cmd/clipx/main.go:198:	cmdPeers		0.0%
github.com/gomantics/clipx/cmd/clipx/main.go:213:	cmdStatus		0.0%
github.com/gomantics/clipx/cmd/clipx/main.go:240:	cmdUpdate		0.0%
github.com/gomantics/clipx/cmd/clipx/main.go:297:	launchAgentPath		0.0%
github.com/gomantics/clipx/cmd/clipx/main.go:302:	logFilePath		0.0%
github.com/gomantics/clipx/cmd/clipx/main.go:307:	cmdInstall		0.0%
github.com/gomantics/clipx/cmd/clipx/main.go:358:	cmdUninstall		0.0%
total:							(statements)		26.8%