chore(release): prepare 0.6.0

[vannt-dev]

Release 0.6.0 with the changes merged in #5:

• The guard hook blocks case variants and Windows trailing-dot/short-name aliases of protected .junto/ evidence paths.
• In a Git repository root, command gate verdicts are bound to source contents outside staleIgnore, so edits that bypass the edit hooks (Bash, formatters, codegen) make them stale.
• Rule obligations and phase transitions are written under the task lock; done is refused if a required gate was invalidated during the transition.
• Review gates reject reserved Windows device names.
• Requires Node.js 22.12 or newer; @modelcontextprotocol/sdk 1.30.1.

This PR updates the plugin, marketplace, package and MCP server versions, rebuilds the bundled server, dates the changelog (adding the missing 0.5.0 and new 0.6.0 compare links), and updates the README and site version.

Validation: typecheck passed; corepack pnpm test — 378 passed, 4 platform/optional skips. A clean git archive of this branch was installed as a directory marketplace in an isolated Claude config (claude plugin install junto@junto, version 0.6.0), and an MCP consumer smoke against the installed plugin passed: server version, small and deep lifecycles, premature finish and required-gate blocks, hook staleness, simulated approval hook, a Bash-style edit blocking done through the source-bound command gate, and guard denial of .JUNTO/active.

After merge: tag v0.6.0 and junto--v0.6.0 on the merge commit, create the GitHub Release, and verify the public marketplace install.