fix: expose Polymarket auth initialization in SDKs

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Fixes #505

Changes

• add Polymarket.initAuth() to the TypeScript SDK
• generate Polymarket.init_auth() for the Python SDK so it survives the exchange wrapper generator
• add a small regression test that checks the Python wrapper keeps forwarding to the core initAuth method

Verification

• node core/scripts/generate-python-exchanges.js
• python -m pytest sdks/python/tests/test_public_exports.py
• TypeScript syntax check via typescript.transpileModule on sdks/typescript/pmxt/client.ts
• git diff --check

I couldn't run the full TypeScript package build in this Windows checkout: the clean script uses rm -rf, and generating the missing OpenAPI client locally needs Java, which isn't installed here.

[realfishsam]

PR Review: PASS (NOT VERIFIED)

Reviewed by: evidence-first bot review

What This Does

Exposes Polymarket.initAuth() in both SDKs. This method already exists in core (core/src/exchanges/polymarket/index.ts:142) but was unreachable from Python and TypeScript SDK consumers. The PR:

1. TS SDK: Adds initAuth() to the Polymarket class in client.ts, plus a new sidecarPostRequest() helper on the base Exchange class for POST-only method dispatch.
2. Python SDK: Adds init_auth() via the generate-python-exchanges.js generator (new methods override in OVERRIDES), so the method survives regeneration.
3. Test: Adds an AST-based regression test verifying the generated Python wrapper calls _call_method("initAuth").

A second commit ("sync generated SDK surfaces") brings the branch up to date with current generator output -- this is unrelated to initAuth but all 6 CI checks pass, confirming it matches what the generators produce.

Blast Radius

In scope (commit 1):

• core/scripts/generate-python-exchanges.js -- generator learns methods override
• sdks/python/pmxt/_exchanges.py -- generated file, now includes init_auth()
• sdks/typescript/pmxt/client.ts -- new sidecarPostRequest() on base class + initAuth() on Polymarket
• sdks/python/tests/test_public_exports.py -- regression test

Out of scope but legitimate sync (commit 2):

• sdks/python/pmxt/client.py -- removes _convert_params_to_camel from 5 methods, changes 9 return type annotations from specific types (MatchResult, PriceComparison, etc.) to List[Any]
• sdks/typescript/pmxt/client.ts -- fetchMarketsPaginated param type MarketFetchParams -> any
• Both API_REFERENCE.md files -- adds cursor to EventFetchParams, subaccount param to GetBalance

Findings

1. MEDIUM -- sidecarPostRequest duplicates existing POST logic
The new sidecarPostRequest() helper on the TS base Exchange class duplicates the POST fallback path already in sidecarReadRequest() (lines 597-610). This is functionally correct but adds ~20 lines of near-identical error handling. Not blocking, but worth noting for future consolidation.

2. LOW -- Python init_auth returns None explicitly
The generated Python method does self._call_method("initAuth") then return None. The _call_method already returns the parsed response (which will be None/undefined for a void method). The explicit return None is harmless but redundant.

3. INFO -- Type annotation downgrades in commit 2
Nine Python return types changed from specific classes (List[MatchResult], List[PriceComparison], List[ArbitrageOpportunity]) to List[Any], and one TS param type from MarketFetchParams to any. These pass CI ("Verify client.py/ts methods are up-to-date"), meaning the generators now produce these looser types. This is a separate concern from initAuth -- the contributor is just syncing to match generator output.

PMXT Pipeline Check

• Field propagation: N/A (no new data fields)
• OpenAPI sync: N/A (initAuth is Polymarket-specific, not a BaseExchange method, so no OpenAPI spec change needed)
• Type safety: OK (both SDKs dispatch to the correct core method; no type mismatches on the initAuth path)
• Auth safety: OK (initAuth stores credentials server-side only; the response is void/undefined -- no credentials flow back through the HTTP response to the SDK)

Semver Impact

Minor -- additive new public method on Polymarket class in both SDKs. No breaking changes. Backward-compatible.

Risk

Low. The initAuth path is additive and only fires when explicitly called by the user. The sync changes in commit 2 are generator-validated by CI. The only concern is the type annotation downgrades (specific types to Any), but those are a pre-existing generator concern, not introduced by this PR's intent.

Core builds. TS SDK type-checks clean. All 6 CI checks pass.