chore: remove context7 integration (tldraw#8934)

In order to drop the Context7 docs integration from the repo, this PR
removes the `context7.json` registration file (which pointed the repo at
context7.com with a public key) and deletes the two `mcp__Context7__*`
permission entries from `.claude/settings.json`. These were the only
references to Context7 in the repository.

### Change type

- [x] `other`

### Test plan

- No user-facing behavior; nothing to test manually.

### Release notes

- Omit — internal tooling change with no user-facing impact.

Author: steveruizok

.claude/settings.json

@@ -34,9 +34,7 @@
 			"Bash(yarn test:*)",
 			"Bash(yarn lint:*)",
 			"Bash(yarn typecheck)",
-			"Bash(git add:*)",
-			"mcp__Context7__resolve-library-id",
-			"mcp__Context7__get-library-docs"
+			"Bash(git add:*)"
 		]
 	},
 	"hooks": {