Bump @typespec/http-client-python catalog to ^0.29.0 (#4413)

## Problem

All Python CI runs are consistently failing with 2 test failures:
- `test_put_model_property` (sync) in
`test_azure_client_generator_core_client_default_value.py`
- `test_put_model_property` (async) in
`test_azure_client_generator_core_client_default_value_async.py`

The error is:
```
Body provided doesn't match expected body: at $: Key count mismatch: expected 4 but got 1. missing: [timeout, tier, retry]
```

## Root Cause

The catalog specifies `@typespec/http-client-python: ^0.28.3`. For 0.x
semver, `^0.28.3` means `>=0.28.3 <0.29.0`, so version `0.29.0` (which
contains the `@clientDefaultValue` serialization fix from
[microsoft/typespec#10546](microsoft/typespec#10546))
is excluded.

The `azure-http-specs` mock API was updated to validate that
`@clientDefaultValue` defaults are included in request bodies, but the
installed generator version (0.28.3) doesn't serialize them.

## Fix

- Bump catalog to `^0.29.0`
- Add `@typespec/http-client-python` to `minimumReleaseAgeExclude`
(0.29.0 was published <2 days ago)

---------

Co-authored-by: iscai-msft <isabellavcai@gmail.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: 3 people

.chronus/changes/bump-http-client-python-catalog-2026-05-12-12-44-33.md

@@ -0,0 +1,7 @@
+---
+changeKind: dependencies
+packages:
+  - "@azure-tools/typespec-python"
+---
+
+Bump @typespec/http-client-python from ^0.28.3 to ^0.29.0

pnpm-lock.yaml

@@ -16,6 +16,7 @@ overrides:
 minimumReleaseAge: 2880 # 2 days
 minimumReleaseAgeExclude:
   - "@alloy-js/*"
+  - "@typespec/http-client-python"
 
 catalog:
   "@alloy-js/cli": ^0.23.0
@@ -85,7 +86,7 @@ catalog:
   "@typescript-eslint/rule-tester": ^8.58.1
   "@typescript-eslint/types": ^8.58.1
   "@typescript-eslint/utils": ^8.58.1
-  "@typespec/http-client-python": ^0.28.3
+  "@typespec/http-client-python": ^0.29.0
   "@typespec/ts-http-runtime": "0.3.4"
   "@vitejs/plugin-react": ^6.0.1
   "@vitest/coverage-v8": ^4.1.3