fix(cpp): build and repair asset::AssetContext

[sunli829]

The bug

longbridge.hpp has always included asset_context.hpp, so C++ users could see asset::AssetContext — but cpp/src/asset_context.cpp was never listed in cpp/CMakeLists.txt. The class was declared to users and then failed to link.

Because it was never built, three separate problems had accumulated behind the missing build entry.

1. lb_statement_item_t was not in the generated header

CStatementItem is only reachable through the void* async-result pointer, so cbindgen never emitted it and no C or C++ caller could read what lb_asset_context_statements returns. Exported it the same way the GridContext payloads already are.

CAssetContext was also missing from the rename map — every other context type was mapped, so the header exposed the raw Rust name while the C++ side forward-declares lb_asset_context_t:

// before
const struct CAssetContext *lb_asset_context_new(const struct lb_config_t *config);
// after
typedef struct lb_asset_context_t lb_asset_context_t;
const struct lb_asset_context_t *lb_asset_context_new(const struct lb_config_t *config);

2. asset_context.cpp did not include the C header

Every other context source includes longbridge.h. This one included only its own .hpp, which forward-declares lb_asset_context_t as an opaque struct and nothing else — so lb_asset_context_retain and friends were undeclared:

error: 'lb_asset_context_retain' was not declared in this scope

3. statement_download_url decoded the wrong shape

It read res->data as a lb_statement_download_url_response_t* and took ->url. No such type exists anywhere in the C layer. lb_asset_context_download_url resolves a CString, so the callback receives the URL as a bare const char* — the same convention as QuoteContext::quote_level:

-  auto resp = (const lb_statement_download_url_response_t*)res->data;
-  StatementDownloadUrlResponse result;
-  result.url = resp->url;
+  StatementDownloadUrlResponse result;
+  result.url = (const char*)res->data;

Verification

• asset_context.cpp.o now builds, and liblongbridge_cpp.so exports the asset::AssetContext symbols.
• statements checked against a live environment: returns the same empty list the Rust core returns for the same account.
• statement_download_url is compile- and link-checked only — the test account has no statement, so there is no file_key to exercise it with. It follows the same (const char*)res->data convention as quote_level, but this has not been confirmed against a real response.
• cargo clippy --all --all-features and cargo +nightly fmt --all clean; full CMake build with 0 errors.

Notes

Independent of #579 — both branch off main and touch disjoint files, except that both add an entry at the top of CHANGELOG.md, so whichever merges second will need a trivial conflict resolution.

🤖 Generated with Claude Code

[sunli829]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Resolved by merging origin/main into this branch and fixing the CHANGELOG.md conflict in commit 616a0119.