Ada→C++ migration phase 1: ADO core, Parameters, SQL + parity tests

[vibhaseshadri-cognition]

Summary

Kicks off an incremental Ada → C++17 port of Ada Database Objects, living side by side with the Ada sources under cpp/. This PR ports the dependency-free foundation (manifest phase 1) and sets up the structure for every later slice.

Ported (Ada → C++)

• ADO → ado.hpp (Identifier, EntityType, ObjectId, Nullable<T>, Blob/BlobRef, Time)
• ADO.Utils, ADO.Dialects → utils.hpp, dialects.hpp (abstract Dialect with default string/bool escaping)
• ADO.Parameters → parameters.hpp: Parameter = std::variant over the Ada discriminated record; AbstractList/List; Expander interface; expand() reproduces the Ada expander exactly (?, :nnn, :name, $group[name], \x escapes; missing param → "").
• ADO.SQL → sql.hpp: Buffer (reserved-name quoting), Query, UpdateQuery (save_field/append_fields update+insert modes), read_file.
• Util.Log replaced by a minimal pluggable sink (log.hpp) — no external deps.

Parity tests — regtests/src/ado-parameters-tests.adb and ado-sql-tests.adb are mirrored in cpp/tests/ with expected strings copied verbatim (incl. Long_Float'Image → ' 1.50000000000000E+00', Calendar.Formatting.Image fraction format). Extra Buffer/Query/UpdateQuery generation tests added. All pass under -Wall -Wextra -Wpedantic -Werror:

ctest --test-dir cpp/build
100% tests passed, 0 tests failed out of 2

Migration scaffolding

• cpp/MIGRATION.md: type-mapping table, 7-phase manifest of all 32 Ada packages + drivers (LOC, target, status), component notes.
• cpp/PORTING_PLAYBOOK.md: phased, verifiable per-package porting procedure to reuse for each subsequent PR.
• .github/workflows/cpp.yml: g++/clang++ CMake build + ctest (path-filtered to cpp/).
• README section pointing to the port.

Notes for reviewers: Identifier is long long (not int64_t) so bind_param(Identifier) resolves unambiguously against the Long_Long_Integer overload on Linux. Named parameters occupy list positions, so ? counts them — this matches Ada and is asserted in test_query.

No Ada sources or Ada regtests were modified.

Devin-Org: engineering

Link to Devin session: https://app.devin.ai/sessions/a807609f1fdf4ecea7e14dfb45a8f2b1
Open in Devin Desktop: https://app.devin.ai/desktop/session/a807609f1fdf4ecea7e14dfb45a8f2b1?variant=devin
Requested by: @vibhaseshadri-cognition

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