fix(db,topics): time.Time params for TIMESTAMP + comment-aware SQL split

Two fixes surfaced by sim e2e test (which otherwise passed full
lifecycle: created → signup_open → 3 signups → allocator → debating
→ arguments → verdict gate (409 early, 201 after debate_end_at) →
completed).

1) MySQL TIMESTAMP rejects RFC3339-with-Z strings — passing those as
   sqlx parameters fails with "Incorrect datetime value". Changed
   CreateTopicInput lifecycle fields from string to time.Time; the
   handler parses+UTCs in validateLifecycleTimes (which now returns
   the parsed array along with the validation result) and passes
   time.Time to the store. The mysql driver formats correctly.

2) splitSQL was naive `strings.Split(s, ";")` which split inside
   comments — the 001 migration had a few `--` lines containing `;`
   ("signup_close_at; immutable", etc) which broke. Migration text
   tidied to not use `;` inside comments, AND splitSQL upgraded to
   skip both `-- ...` and `/* ... */` comment regions before splitting.

Sim verified — clean apply on fresh MySQL.

internal/db/db.go

@@ -105,10 +105,33 @@ func RunMigrations(ctx context.Context, d *sqlx.DB) error {
 }
 
 func splitSQL(s string) []string {
-	// Crude but adequate for our migrations (no string-literal semicolons).
-	// If we ever need to embed semicolons inside strings, switch to a
-	// proper SQL tokenizer.
-	return strings.Split(s, ";")
+	// Comment-aware splitter: skip `;` inside `-- ...` line comments
+	// and `/* ... */` block comments. Doesn't handle string-literal
+	// semicolons (we don't put any) — if we ever need that, swap in a
+	// real SQL tokenizer.
+	var b strings.Builder
+	i := 0
+	for i < len(s) {
+		if i+1 < len(s) && s[i] == '-' && s[i+1] == '-' {
+			// single-line comment — strip through end of line
+			for i < len(s) && s[i] != '\n' {
+				i++
+			}
+			continue
+		}
+		if i+1 < len(s) && s[i] == '/' && s[i+1] == '*' {
+			// block comment — strip through `*/`
+			i += 2
+			for i+1 < len(s) && !(s[i] == '*' && s[i+1] == '/') {
+				i++
+			}
+			i += 2
+			continue
+		}
+		b.WriteByte(s[i])
+		i++
+	}
+	return strings.Split(b.String(), ";")
 }
 
 func firstLine(s string) string {

internal/db/migrations/001_init.sql

@@ -1,7 +1,7 @@
 -- 001_init.sql — Dialectic v2 schema (greenfield, replaces Python v1).
 -- See /home/hzhang/arch/DIALECTIC-V2-DESIGN.md for the design.
 
--- Verdict schemas — declared at topic-creation time; judge produces output matching.
+-- Verdict schemas — declared at topic-creation time, judge produces output matching.
 CREATE TABLE verdict_schemas (
     id          VARCHAR(64)  NOT NULL PRIMARY KEY,
     description TEXT         NOT NULL,
@@ -60,7 +60,7 @@ CREATE TABLE signups (
 
 -- Camps: the post-allocation assignment. One row per (topic, camp) with
 -- the locked-in agent. Written by camp-allocation algorithm at
--- signup_close_at; immutable afterwards (no drop-out / replacement in v1).
+-- signup_close_at — immutable afterwards (no drop-out / replacement in v1).
 CREATE TABLE camps (
     id              CHAR(36)     NOT NULL PRIMARY KEY,
     topic_id        CHAR(36)     NOT NULL,
@@ -73,7 +73,7 @@ CREATE TABLE camps (
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
 
 -- Rounds: chronological partition of arguments. Each topic has N rounds
--- (typically 3-5); round 0 is the opening. Round transitions are driven
+-- (typically 3-5), round 0 is the opening. Round transitions are driven
 -- by the orchestrator on a schedule (or all-participants-posted).
 CREATE TABLE rounds (
     id              CHAR(36)     NOT NULL PRIMARY KEY,
@@ -86,7 +86,7 @@ CREATE TABLE rounds (
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
 
 -- Arguments: an individual contribution within a round by a camp's agent.
--- For pro/con these are claims/rebuttals; for judge these are clarifying
+-- For pro/con these are claims/rebuttals — for judge these are clarifying
 -- questions (judge is silent observer in v1 except for clarifications).
 CREATE TABLE arguments (
     id              CHAR(36)     NOT NULL PRIMARY KEY,
@@ -118,7 +118,7 @@ CREATE TABLE verdicts (
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
 
 -- Agent API keys: provisioned per agent at recruitment time. Stored as
--- sha256(pepper || raw); pepper rotation invalidates all keys.
+-- sha256(pepper || raw) — pepper rotation invalidates all keys.
 CREATE TABLE agent_keys (
     agent_id       VARCHAR(64)  NOT NULL PRIMARY KEY,
     key_hash       CHAR(64)     NOT NULL UNIQUE,