S00-012: Record blocked task and remediation handoff

Changes: Preserve incomplete work and blocker metadata for S00-012. This checkpoint does not mark implementation accepted.
Validation: Session ended with status blocked.
Blocker: Required automation suite fails in existing all-prompts budget test: S21-006 exceeds even a diagnostic 90000-character prompt limit. This blocks verification of the stdin remediation; production limit remains 80000.

Task: S00-012
Agent: manual-ci-cd-stdin-20261015b
Role: ci-cd
Action: escalate
Status: blocked

Task title: Fix runner prompt delivery after partial stdin timeout

planning/tasks.json

@@ -216,7 +216,8 @@
       "outcome": "ADR сравнивает два допустимых стека, фиксирует конкретные проверенные versions, lockfile и один минимальный rendering spike.",
       "depends_on": [
         "S00-001",
-        "S00-011"
+        "S00-011",
+        "S00-012"
       ],
       "requirements": [
         "NFR-007"
@@ -668,6 +669,114 @@
       ],
       "context_budget_chars": 48000
     },
+    {
+      "id": "S00-012",
+      "stage": "S00",
+      "kind": "blocker",
+      "root_task": "S00-002",
+      "blocker_depth": 1,
+      "unblocks": [
+        "S00-002"
+      ],
+      "role": "ci-cd",
+      "reviewer_role": "qa",
+      "title": "Fix runner prompt delivery after partial stdin timeout",
+      "outcome": "Reliable complete prompt delivery under startup delay and pipe backpressure, preserving runner lifecycle guarantees.",
+      "depends_on": [
+        "S00-001",
+        "S00-011",
+        "S00-013"
+      ],
+      "requirements": [
+        "NFR-007"
+      ],
+      "scope": [
+        "scripts/runner.py",
+        "tests/tooling/test_automation.py"
+      ],
+      "inputs": [
+        "docs/WEB_PROFILE.md",
+        "docs/ARCHITECTURE.md",
+        "docs/CONTRACTS.md",
+        "docs/TESTING.md",
+        "roles/orchestrator.md",
+        "docs/decisions/README.md",
+        "state/blockers/S00-012.md"
+      ],
+      "spec_sections": [],
+      "ui_sections": [],
+      "steps": [
+        "Read diagnostic evidence and reproduce delayed-reader partial-write timeout without launching a model.",
+        "Fix only runner stdin delivery; retain fresh sessions, prompt budget, terminal-transition monitoring, timeout and process-tree cleanup.",
+        "Add a deterministic delayed-reader large-prompt regression check and run focused runner tests plus make check.",
+        "Record evidence/handoff/commit message and submit for independent review."
+      ],
+      "acceptance": [
+        "A delayed stdin reader receives the complete large UTF-8 prompt and EOF without hanging.",
+        "Timeout and terminal-transition process cleanup still work; no background source-writing descendants remain.",
+        "Existing runner/tooling checks pass; no task scope, spec snapshots or product implementation is changed."
+      ],
+      "checks": [
+        "Delayed-reader large UTF-8 prompt regression.",
+        "Existing runner timeout, transition, scope and fresh-session tests.",
+        "make check"
+      ],
+      "context_budget_chars": 48000
+    },
+    {
+      "id": "S00-013",
+      "stage": "S00",
+      "kind": "blocker",
+      "root_task": "S00-002",
+      "blocker_depth": 2,
+      "unblocks": [
+        "S00-012"
+      ],
+      "role": "ci-cd",
+      "reviewer_role": "qa",
+      "title": "Bound oversized S21-006 runner context without truncating requirements",
+      "outcome": "All task prompts fit the existing configured budget with exact relevant requirements retained and no silent truncation.",
+      "depends_on": [
+        "S00-001",
+        "S00-011"
+      ],
+      "requirements": [
+        "NFR-007"
+      ],
+      "scope": [
+        "scripts/runner.py",
+        "tests/tooling/test_automation.py"
+      ],
+      "inputs": [
+        "docs/WEB_PROFILE.md",
+        "docs/ARCHITECTURE.md",
+        "docs/CONTRACTS.md",
+        "docs/TESTING.md",
+        "roles/orchestrator.md",
+        "docs/decisions/README.md",
+        "state/blockers/S00-012.md",
+        "state/blockers/S00-013.md"
+      ],
+      "spec_sections": [],
+      "ui_sections": [],
+      "steps": [
+        "Inspect S21-006 prompt inputs and identify unnecessary duplication or overly broad context loading.",
+        "Implement one bounded context-preparation correction while preserving assignment instructions and exact relevant requirements; retain stdin transport changes.",
+        "Add focused regression for the real oversized context and run existing prompt-budget checks and make check.",
+        "Record evidence/handoff/message and submit for independent review."
+      ],
+      "acceptance": [
+        "S21-006 and all current task prompts fit the existing 80000-character limit.",
+        "Exact required context is retained; no spec snapshot edits, silent truncation or validation suppression.",
+        "stdin delivery, timeout and terminal-transition regression checks remain passing; make check passes."
+      ],
+      "checks": [
+        "Existing FoundationRunnerTests all-current-prompts budget check.",
+        "Delayed UTF-8 stdin delivery and runner lifecycle tests.",
+        "make check"
+      ],
+      "context_budget_chars": 48000
+    },
     {
       "id": "S00-010",
       "stage": "S00",