chore: release v0.2.0

[amcheste-ai-agent]

Minor bump (0.1.0 → 0.2.0). This release introduces a `feat:` commit (the brand banner from #20), and per the handbook rule `feat` → minor, so this is 0.2.0, not 0.1.1.

What's in this release

Added

• Brand banner under `assets/` (svg + 1200/2400 png) per `banner-spec.md`. Hero shows the four philosophy pillars with a Hunter Green δ marker on Branching. Inline `<style>` block bakes IBM Plex Sans/Mono/Serif metrics into the SVG so it renders standalone on GitHub.
• "GitHub default branch setting" subsection in Branching & Releases, clarifying that the integration trunk (always `develop`) is distinct from GitHub's "default branch" repo setting (develop pre-release, main post-release).
• Step 5 in the release ceremony: ensure `main` is the GitHub default branch. Idempotent — only takes effect on the first release.
• Brand-aligned README badges (license in Hunter Green, version in Ink).

Changed

• Release Drafter workflow bumped to v7.3.0 (`c2e2804`). Dropped the `pull_request` trigger — v7 was failing CI on PR events because `GITHUB_REF` is `refs/pull/N/merge`, which the Releases API rejects as `target_commitish`.

Fixed

• Banner SVG `.stack` text overflow into the monogram (fix(banner): shrink .stack text to clear the monogram #22).
• Scorecard workflow imposter `github/codeql-action/upload-sarif` SHA replaced with the real v4 pin. Added `publish_results` condition keyed to `default_branch`.

Release ceremony

This PR is Step 1 of `/publish-release`. Merge it, then the rest runs on CLI:

• Step 2: `git merge --no-ff origin/develop` into main, push main
• Step 3: tag `v0.2.0` annotated, push tag
• Step 4: confirm release pipeline triggered
• Step 5: ensure `main` is the GitHub default branch (already is — second release, no-op)

No code changes — docs + assets only.