chore: migrate repo-location refs from Gerrrt to dotgibson org

[Gerrrt]

What

Part of the org migration Gerrrt → dotgibson. Rewrites hardcoded repo-location references across Core's vendored-out surface:

• URLs — .bin/sync-upstream.sh (CORE_REPO_URL), ARCHITECTURE.md (subtree example)
• Reusable-workflow uses: refs — auto-tag-call.yml, bootstrap-test.yml, core-integrity-call.yml
• github.repository_owner guards — release.yml, sync-fanout.yml, notify-web.yml (these silently no-op under any other owner, so they must move with the org)
• notify-web dispatch URL → api.github.com/repos/dotgibson/dotfiles-web/dispatches
• Showcase Pages badge — gerrrt.github.io → dotgibson.github.io

Deliberately NOT changed (personal handle, not repo locations)

• nvim Lua namespace nvim/lua/gerrrt/** — renaming breaks require()
• @gerrrt in CODEOWNERS
• CHANGELOG history entries

Verification

make audit → pass 231, skip 0, fail 0 (full toolchain: shellcheck, actionlint, markdownlint, luacheck, gitleaks, zsh behavioral suite).

Fan-out

After merge, make sync fans this into every OS repo's core/ — no vendored core/ tree is hand-edited.

🤖 Generated with Claude Code

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Generated by Claude Code

[Copilot]

Pull request overview

This PR is part of the Gerrrt → dotgibson organization migration. It rewrites hardcoded repo-location references across Core's vendored-out surface — repo URLs, reusable-workflow uses: refs (in doc comments), github.repository_owner guards, the notify-web dispatch URL, and the showcase Pages badge — so they point at the new org. Personal-handle references (the nvim lua/gerrrt/** namespace and @gerrrt code-owner) are deliberately left unchanged since renaming them would break require() and ownership, respectively.

Changes:

• Migrated repo URLs and subtree/dispatch endpoints (.bin/sync-upstream.sh, ARCHITECTURE.md, notify-web.yml) and the showcase badge (README.md) to dotgibson.
• Updated the functional github.repository_owner == 'dotgibson' guards in release.yml, sync-fanout.yml, and notify-web.yml, plus documentation uses: refs in the reusable-workflow headers.
• Recorded the migration in CHANGELOG.md under [Unreleased].

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
README.md	Showcase Pages badge URL gerrrt.github.io → dotgibson.github.io.
CHANGELOG.md	Adds an [Unreleased] entry documenting the migration and the deliberate exclusions.
ARCHITECTURE.md	Updates the git subtree add example URL to the new org.
.bin/sync-upstream.sh	Points CORE_REPO_URL at the new org.
.github/workflows/release.yml	Owner guard Gerrrt → dotgibson.
.github/workflows/sync-fanout.yml	Owner guard Gerrrt → dotgibson.
.github/workflows/notify-web.yml	Owner guard, setup comment, and dispatch URL updated to new org.
.github/workflows/auto-tag-call.yml	Doc-comment uses: ref updated.
.github/workflows/bootstrap-test.yml	Doc-comment uses: ref updated.
.github/workflows/core-integrity-call.yml	Doc-comment uses: ref updated.

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