docs(track-a): add native login-to-ingame prompt

[blakinio]

Objective

Persist the reviewed Track A native semantic login-to-ingame worker prompt and short alias.

Scope

Documentation/prompting only. No official-client runtime, credentials, workflow, client binary, PR #475 runtime, or predecessor #498/#499 branches are modified.

Added surfaces

• docs/agents/prompts/OTCLIENT_TIBIA_RE_NATIVE_LOGIN_TO_INGAME.md
• docs/agents/prompts/OTCLIENT_TIBIA_RE_NATIVE_LOGIN_TO_INGAME_ALIAS.md
• docs/agents/tasks/active/OTC-20260817-track-a-native-login-to-ingame-prompt.md

Hardening included

• predecessor research(track-a): recover native auth and session flow #498/research(track-a): prove native game-login credential fields #499 provenance is fail-closed until exact-SHA/runtime revalidation;
• serialized Track A runtime ownership, including runtime(track-a): validate causal worldmap server delivery #475, cannot be preempted or consumed implicitly;
• static VA/RVA must be rebound through the current PIE/ELF mapping before direct calls;
• SysV AMD64/Itanium ABI, object lifetime and Qt thread affinity are explicit invocation gates;
• credential ingress via argv/env/GDB command text/history/logs/artifacts is forbidden; protected transient ingress is required;
• valid retained session is preferred over unnecessary password use;
• target character is resolved semantically and uniquely;
• server login success and screenshots are insufficient for completion;
• cross-layer gameplay state + active local player + downstream gameplay + character/world identity are required for causal IN_GAME;
• anti-stall ROTATE|WAITING|BLOCKED remains a worker outcome and never weakens task-success criteria.

Validation

• manual prompt-eval matrix: PASS 12/12;
• proportionate fresh content falsification: PASS, material findings 0;
• changed-file inventory: exactly the three declared documentation/prompting paths;
• full PR patch review: PASS, no unrelated/runtime/workflow/binary/credential changes;
• runtime E2E: NOT_APPLICABLE_WITH_REASON — this PR persists prompting documentation only and performs no client/runtime operation;
• exact-head GitHub checks: required before merge.

Prompt contract: 2.0.0. Alias: OTCLIENT-TIBIA-RE-NATIVE-LOGIN-TO-INGAME.