fix(packaging): align React peer ranges for clean npm installs

[ScriptedAlchemy]

Problem

A clean npm consumer that installs agent-bundle with @agent-bundle/runtime can fail with ERESOLVE now that React 19.3.0 is published.

agent-bundle declares an exact optional peer:

"react": "19.2.8"

while @agent-bundle/runtime declares:

"react": "^19.2.0",
"react-dom": "^19.2.0"

Without React preinstalled, npm selects React/React DOM 19.3.0 for the runtime and then rejects agent-bundle's exact React 19.2.8 peer. This is a pre-existing manifest inconsistency surfaced while triaging #777; it is not caused by the rslint bump.

#777 pins React 19.2.8 and React DOM 19.2.8 in generated routed templates and in the packed bin-consumer harness. That restores release coverage for the supported consumer state, but the harness pin also stops the clean-consumer proof from detecting peer-range drift.

Acceptance

• Align or safely widen the agent-bundle and @agent-bundle/runtime React peer ranges so a clean npm install resolves without explicit React preinstallation.
• Preserve React/React DOM version compatibility rather than bypassing peer checks with --legacy-peer-deps or --force.
• Remove the explicit React pins from scripts/run-packed-tests.mjs so its clean-consumer install detects future peer drift again.
• Add a regression test for the clean npm consumer install.
• Update the matching English and Chinese installation guidance.
• Include exactly one changeset for the affected publishable package(s).