[BUG] Claude for Excel (Bedrock direct) selects us. inference profile when manifest aws_region is eu-west-1, causing 400/404 at bedrock-runtime.eu-west-1.amazonaws.com

Origionally posted by @siddharthmishrasm under [Claude-code](https://github.com/anthropics/claude-code/issues/51074#issue-4294607829)

### What's Wrong?

When the `claude-in-office` manifest is provisioned with `aws_region: eu-west-1` for the Bedrock direct path, the add-in constructs invoke URLs of the form:

```
https://bedrock-runtime.eu-west-1.amazonaws.com/model/us.anthropic.claude-opus-4-7/invoke
```

This is an invalid combination. The `us.` cross-region inference profile only exists in and routes to `us-east-1`, `us-east-2`, and `us-west-2`. It is not resolvable from a `bedrock-runtime.eu-west-1.amazonaws.com` endpoint, so every request fails.

The root cause appears to be that the add-in's model selection logic is not region-aware: it picks a `us.`-prefixed inference profile regardless of the configured `aws_region`.

### Why admins cannot work around this

Per the [third-party platforms documentation](https://support.claude.com/en/articles/13945233-use-claude-for-excel-powerpoint-and-word-with-third-party-platforms) and the `claude-in-office` manifest spec, admins can configure `aws_region` but cannot pin a specific inference profile ID. The add-in discovers and selects the model at runtime. That means this bug cannot be worked around through manifest configuration — it requires a code fix.

### What Should Happen?

When `aws_region` is an EU region, the add-in should select a compatible profile:
- An `eu.`-prefixed geographic CRIS profile if one exists for the target model (e.g., `eu.anthropic.claude-opus-4-6-v1` for Opus 4.6), or
- A `global.`-prefixed profile (e.g., `global.anthropic.claude-opus-4-7`) when no `eu.` profile exists and the source region supports global CRIS (eu-west-1 does).

Symmetrically for `apac.` / APAC regions.

### Error Messages/Logs

```shell
Claude for Office connection failed (Bedrock)
Build: *****

400 The provided model identifier is invalid.

Request:
aws_role_arn: arn:aws:iam::*********:role/ClaudeBedrockAccess
aws_region: eu-west-1

Manifest params:
m: unified-1.0.0.12
aws_role_arn: arn:aws:iam::********:role/ClaudeBedrockAccess
aws_region: eu-west-1
entra_sso: 1
et:

Bootstrap response:
(not called)

Raw error:
400 The provided model identifier is invalid.
```

### Steps to Reproduce

1. Run `/claude-in-office:setup` and configure the Bedrock direct path with `aws_region: eu-west-1`.
2. Ensure the signed-in AWS role has access to `eu.` and/or `global.` inference profiles in eu-west-1 (verified working via AWS CLI `bedrock-runtime invoke-model`).
3. Deploy the manifest and open Claude for Excel.
4. Sign in via Entra ID.
5. Any prompt fails with an invocation error against `https://bedrock-runtime.eu-west-1.amazonaws.com/model/us.anthropic.claude-opus-4-7/invoke`.

### Expected Behavior

The add-in selects an inference profile whose source-region list includes the configured `aws_region`, and successfully invokes the model.

### Actual Behavior

The add-in selects `us.anthropic.claude-opus-4-7` (or similar `us.`-prefixed profile) and sends it to the eu-west-1 endpoint, resulting in a 400/404.

### Claude Model

Opus

### Is this a regression?

No, this never worked

### Last Working Version

_No response_

### Claude Code Version

2.1.113

### Platform

AWS Bedrock

### Operating System

macOS

### Terminal/Shell

Terminal.app (macOS)

### Additional Information

_No response_