feat: enable memory in agentcore dev

[avi-alpert]

Description

Enables memory support in agentcore dev by injecting deployed memory IDs as environment variables into the local dev server process. Previously, the dev server showed a blanket warning that memory was unavailable locally. Now, if memories have been deployed via agentcore deploy, their IDs are read from deployed state and passed as MEMORY_<NAME>_ID env vars — allowing agents to use memory during local development.

Changes:

• Add memory-env.ts module that reads deployed state and generates MEMORY_*_ID env vars from all deployment targets
• Merge memory env vars into the dev server environment (alongside gateway env vars), with .env.local overrides taking precedence
• Replace the blanket "memory not available locally" warning with a smarter check that only warns when configured memories haven't been deployed yet
• Update warning copy to guide users: "run agentcore deploy and restart dev"
• Add unit tests for getMemoryEnvVars covering deployed memories, multiple targets, missing state, and edge cases

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update
• Other (please describe):

Testing

How have you tested the change?

• I ran npm run test:unit and npm run test:integ
• I ran npm run typecheck
• I ran npm run lint
• If I modified src/assets/, I ran npm run test:update-snapshots and committed the updated snapshots

Manual testing was done with a Strands agent only. Other agent frameworks have not been tested.

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• My changes generate no new warnings
• Any dependent changes have been merged and published

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