Add Tiny Tool Town submission canvas (#2240)

* Add Tiny Tool Town submission canvas

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

* Add generated description choices

Resolve picker opens from the active session working directory so linked worktrees work without an explicit repository path.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

* Address Tiny Tool review comments

Detect root .csproj files as build signals and hide canvas access tokens from the visible URL after first load.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

* Address latest Tiny Tool review comments

Handle root-relative README images, preserve drafts during refresh, and suppress GitHub mentions before public issue creation.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

* Address canvas shutdown and CSP review

Close all canvas servers during shutdown, use nonce-based CSP, make theme optional, and hide decorative preview dots from assistive tech.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

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Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

extensions/tiny-tool-town-submitter/.github/plugin/plugin.json

@@ -0,0 +1,19 @@
+{
+  "name": "tiny-tool-town-submitter",
+  "description": "Inspect a repository, improve Tiny Tool Town readiness, submit its listing issue, and launch remediation work.",
+  "version": "1.0.0",
+  "author": {
+    "name": "James Montemagno",
+    "url": "https://github.com/jamesmontemagno"
+  },
+  "keywords": [
+    "github-issues",
+    "open-source",
+    "project-readiness",
+    "repository-analysis",
+    "submission-workflow",
+    "tiny-tool-town"
+  ],
+  "logo": "assets/preview.png",
+  "extensions": "."
+}