fix: remove default ssml config value for cartesia tts

[YiminW]

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[github-actions]

Reviewed. The fix is correct and well-targeted.

I verified the failure it addresses: property.json shipped ssml.enabled: true together with emotion: "angry", and _compose_ssml_text in extension.py only early-returns when enabled is falsy — so every utterance synthesized with the stock config was prefixed with <emotion value="angry"/>. Removing the block makes CartesiaSSMLConfig supply the defaults instead (enabled: bool = False), so no tags are emitted unless a user opts in. Good call keeping the ssml schema in manifest.json: the property stays supported and documented, it just is no longer forced on anyone. The version bumps are consistent — manifest.json and pyproject.toml both go 0.8.2 to 0.8.3.

The fix looks incomplete: three test configs still carry the same block. tests/configs/ still has the identical ssml block, emotion: "angry" included, in property_basic_audio_setting1.json, property_basic_audio_setting2.json, and property_dump.json. These are not dead files: the tts_guarder integration suite loads two of them by name (ai_agents/agents/integration_tests/tts_guarder/tests/test_basic_audio_setting.py defines TTS_BASIC_AUDIO_SETTING_CONFIG_FILE1/2 as exactly those filenames). So after this PR the audio-setting and dump tests still exercise SSML-enabled, angry-emotion synthesis, a configuration that no longer matches anything the extension ships. That is the wrong way round: the tests validating audio output should run the default path, otherwise the regression you just fixed would not be caught if it returned. I would drop the ssml block from all three here, since it is the same edit.

No regression test pins the fix. test_ssml_presets and test_ssml_metadata_overrides both pass ssml explicitly in their inline config, so neither broke nor covers this change. A short test asserting that a config of just {"params": {"api_key": "..."}} reaches the client with text byte-identical to the input would lock the behavior in cheaply — the ExtensionTesterSSML harness already captures t.text.

Latent issue in CartesiaSSMLConfig.merge (pre-existing, not introduced here). merge skips incoming None values, but enabled is a non-optional bool defaulting to False, so a partial patch such as {"ssml": {"emotion": "sad"}} constructs enabled=False and silently overwrites an enabled base. Harmless now that the base default is also False, and this PR incidentally defuses it — but if a preset is ever reintroduced as a default it will bite. Declaring enabled: bool | None = None and resolving to False at read time would close it properly.

Convention nits. Per AGENTS.md, branches are type/short-description, hyphen-separated — dev/cartesia_tts_remove_default_smml uses a dev/ prefix and underscores, and has a typo (smml should be ssml). The commit title itself is formatted correctly. The PR body is empty; one line naming the symptom (all speech rendered angry) would help whoever bisects this later.

No blockers apart from the leftover test configs.