fix(export): match harness allowedTools for customer tools and keep model parameters

[amhegazy-mp4]

Description

agentcore export harness now matches the harness it exports in two places:

• allowedTools for configured tools. A bare pattern (shell, file_*) selects built-in tools only, and @name selects a configured tool (MCP server, inline function, gateway, browser, code interpreter), as the harness does. Previously @name dropped the tool and a bare name kept it. A bare built-in name such as shell now also selects the built-in, which previously required @builtin/shell. matchesAllowedTools now takes the server and tool separately instead of a flattened name.
• Model additionalParams. For bedrock, open_ai, and gemini, export harness --arn carries the harness model's additionalParams into the generated model/load.py (Bedrock additional_args; params for Mantle, OpenAI, and Gemini) instead of dropping them with an export note. Explicit model settings (temperature, max tokens, ...) take precedence. The local harness spec still omits the field, since harness.yaml accepts it only for lite_llm, so the values are passed to the export alongside the spec.

Behavior changes for new exports: a bare configured-tool name in allowedTools no longer keeps that tool (use @name), matching the harness.

Related Issue

Closes #2455

Documentation PR

Not applicable.

Type of Change

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

Testing

• I ran bun test
• I ran the relevant end-to-end tests with bun run test:e2e, or explained why they are not applicable: there are no export end-to-end tests. Instead I rendered an export and ran it against Bedrock: allowedTools: ["@mcp"] kept the MCP server and the model called its tool, and Bedrock accepted the carried-over additionalParams.
• I ran bun run typecheck
• I ran bun run lint:check
• I ran bun run format:check
• I ran bun run build
• If I modified src/assets/, I updated affected snapshots with bun test <test-file> --update-snapshots and committed them (no snapshots changed)

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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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.23%. Comparing base (924ab68) to head (667fe6c).

Additional details and impacted files

@@            Coverage Diff            @@
##           refactor    #2456   +/-   ##
=========================================
  Coverage     97.23%   97.23%           
=========================================
  Files           606      606           
  Lines         42479    42475    -4     
=========================================
- Hits          41304    41301    -3     
+ Misses         1175     1174    -1     

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