Make the postinstall vscode-jsonrpc rewrite conditional, then lift the copilot-sdk cap #2415

Follow-up to #2414, which caps @github/copilot-sdk below 1.0.29 as a mitigation.

Problem

packages/squad-cli/scripts/patch-esm-imports.mjs runs as the CLI postinstall and from squad upgrade (packages/squad-cli/src/cli/core/upgrade.ts:1113-1114). It patches unconditionally:

• Layer 1 replaces the exports map of every vscode-jsonrpc copy in its search roots whose map lacks ./node.js. That includes valid 9.x and 10.x maps. It never sees the copy nested under @github/copilot-sdk/node_modules.
• Layer 2 rewrites vscode-jsonrpc/node to vscode-jsonrpc/node.js in copilot-sdk's dist/session.js.

copilot-sdk 1.0.29 and later depend on vscode-jsonrpc 10, which exports ./node but not ./node.js, so the rewrite breaks the import with ERR_PACKAGE_PATH_NOT_EXPORTED.

Proposed fix

• Rewrite only when the vscode-jsonrpc that session.js actually resolves to has no exports map (8.x). Otherwise leave the import alone. Consider undoing an earlier rewrite when the resolved copy doesn't export ./node.js.
• Add an exports map only to copies that have none. Don't overwrite valid maps.
• Apply the same condition to the squad doctor check (packages/squad-cli/src/cli/commands/doctor.ts:521-539), which currently tells users to run the postinstall whenever the import has no extension.
• Review the runtime resolver hook in packages/squad-cli/src/cli-entry.ts:42-52.
• Add regression tests for an 8.x layout and a nested 10.x layout. Then lift the cap in packages/squad-sdk/package.json and confirm test/cli-packaging-smoke.test.ts passes with copilot-sdk 1.0.29 or later.