feat(WP-0016/C2-C3): close build infrastructure workplan

C2: document actual GHC cache behavior (-fbyte-code, no .o files, .hi
caching via -fwrite-interface) and correct CLAUDE.md cache claim.
C3: create IHUB-WP-0017 error-fix loop workplan (ralph-compatible,
5 tasks E1-E5, runs inside devenv shell).
WP-0016 status → done.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

workplans/IHUB-WP-0017-error-fix-loop.md

@@ -0,0 +1,120 @@
+---
+id: IHUB-WP-0017
+type: workplan
+title: "Autonomous Error-Fix Loop: Reach Clean Build"
+domain: inter_hub
+repo: inter-hub
+status: active
+owner: custodian
+created: "2026-04-10"
+updated: "2026-04-10"
+depends_on: [IHUB-WP-0016]
+---
+
+# IHUB-WP-0017 — Autonomous Error-Fix Loop: Reach Clean Build
+
+## Goal
+
+Drive the inter-hub codebase to a clean `ghcid` build ("All good, N modules loaded")
+by fixing compilation errors bottom-up, one module at a time.
+
+## Pre-conditions
+
+- Must be run inside `devenv shell` (IHP_LIB must be set, ghcid in PATH)
+- WP-0016 complete (compile-check scripts and ghci flags in place)
+
+## How to start
+
+```bash
+# Enter devenv shell first:
+devenv shell
+
+# Then start this loop:
+/ralph-workplan workplans/IHUB-WP-0017-error-fix-loop.md
+```
+
+## Error-Fix SOP (Standard Operating Procedure)
+
+```
+1. Run: scripts/compile-check --bg
+2. Tail /tmp/ihub-compile-errors.txt
+3. Parse errors: group by module, order by Layer (1 → 4)
+4. Fix Layer 1 errors first (rare; usually type/import issues in Web/Types.hs)
+5. For each failing module in Layer 2–3:
+   a. Read current module state
+   b. Apply targeted fix (one module at a time)
+   c. Wait for ghcid "Reloading..." + result
+   d. If still failing: re-read error, apply next fix
+   e. If 3 attempts fail: escalate — flag_for_human with module name and error
+6. After Layer 3 clean: fix Layer 4 (FrontController/Routes)
+7. "All good (N modules)" in log = build clean
+```
+
+**Layer discipline** (never violate):
+- Never modify Layer 1 (`Web/Types.hs`, `build/Generated/*.hs`) during error-fix loops
+- Layer 1 changes invalidate ALL 59 controllers and 120 views simultaneously
+- Fix within the layer where the error is reported; escalate if the fix requires Layer 1
+
+## Tasks
+
+### E1 — Start compile-check and capture initial error set
+
+```task
+id: E1
+status: todo
+priority: high
+```
+
+Run `scripts/compile-check --bg` and read `/tmp/ihub-compile-errors.txt`. List all
+failing modules and their layers.
+
+### E2 — Fix Layer 2 errors (Application/Helper/*.hs)
+
+```task
+id: E2
+status: todo
+priority: high
+```
+
+Fix all errors in `Application/Helper/*.hs`. Verify via ghcid reload. Mark done when
+Layer 2 shows no errors.
+
+### E3 — Fix Layer 3 errors (Web/Controller/*.hs and Web/View/**/*.hs)
+
+```task
+id: E3
+status: todo
+priority: high
+```
+
+Fix errors in controllers and views. Work module-by-module, bottom-up. Mark done when
+Layer 3 shows no errors.
+
+### E4 — Fix Layer 4 errors (Web/FrontController.hs, Web/Routes.hs)
+
+```task
+id: E4
+status: todo
+priority: medium
+```
+
+Fix wiring errors last. Mark done when `ghcid` reports "All good, N modules loaded".
+
+### E5 — Commit clean build and close WP-0014/A1
+
+```task
+id: E5
+status: todo
+priority: medium
+```
+
+After "All good" state:
+1. Commit all fixes with `fix(WP-0017): reach clean build`
+2. Update `workplans/IHUB-WP-0014-pre-flight-deployment-gaps.md` A1 status to done
+3. Mark this workplan done
+
+## Exit Criteria
+
+- `ghcid` reports "All good, N modules loaded" with no errors
+- All fixes committed
+- WP-0014/A1 closed