chore(v0.6): checkpoint foundation — Amber theme, P1 types, P3 config, design docs

Prior-session prep for the v0.6 Project Manager, checkpointed on the
v0.6-projects branch as a clean base for the parallel builders:

- P1 (src/types.ts): ProjectInfo + ProjectSessionRef contracts; Config
  gains projectRoots/projectScanDepth/projectScanTtlMs/projectDirtyCheck.
- P3 (src/config.ts): parseBool + parseProjectRoots helpers; parse the
  4 PROJECT_* env vars with defaults ([homeDir]/4/10000/true).
- UI: public/style.css indigo -> Amber (#e3a64a) accent theme.
- Docs: FEATURE_PROJECT_MANAGER.md (1:N session design), THEME.md,
  docs/mockups/ (final-amber.png is the locked visual).

Typecheck (backend + web) green. No behavior change to runtime code yet;
P2/P4/P5/P6 implement the feature on top of this.

src/config.ts

@@ -31,6 +31,8 @@ const DEFAULT_MAX_MSGS_PER_SEC = 2000
 const DEFAULT_PERM_TIMEOUT_MS = 5 * 60_000 // H3: hold a PermissionRequest for 5 min
 const DEFAULT_REAP_INTERVAL_MS = 60_000 // idle reaper sweeps every minute
 const DEFAULT_PREVIEW_BYTES = 24 * 1024 // manage-page preview: tail of scrollback
+const DEFAULT_PROJECT_SCAN_DEPTH = 4 // v0.6: how deep to scan roots for .git
+const DEFAULT_PROJECT_SCAN_TTL_MS = 10_000 // v0.6: /projects discovery cache TTL
 
 // ── helpers ───────────────────────────────────────────────────────────────────
 
@@ -50,6 +52,27 @@ function parseNonNegativeInt(
   return n
 }
 
+/** Parse a boolean env value ('1'/'true'/'on' → true, '0'/'false'/'off' → false), else fallback. */
+function parseBool(raw: string | undefined, fallback: boolean): boolean {
+  const v = raw?.trim().toLowerCase()
+  if (v === undefined || v === '') return fallback
+  if (v === '1' || v === 'true' || v === 'on') return true
+  if (v === '0' || v === 'false' || v === 'off') return false
+  return fallback
+}
+
+/** Parse PROJECT_ROOTS (comma-separated absolute paths); expand a leading '~' to homeDir.
+ *  Empty / unset → [homeDir]. */
+function parseProjectRoots(raw: string | undefined, homeDir: string): readonly string[] {
+  if (raw === undefined || raw.trim() === '') return Object.freeze([homeDir])
+  const roots = raw
+    .split(',')
+    .map((s) => s.trim())
+    .filter((s) => s !== '')
+    .map((s) => (s === '~' ? homeDir : s.startsWith('~/') ? homeDir + s.slice(1) : s))
+  return Object.freeze(roots.length > 0 ? roots : [homeDir])
+}
+
 function parsePort(raw: string | undefined): number {
   if (raw === undefined) return DEFAULT_PORT
   const n = Number(raw)
@@ -195,6 +218,20 @@ export function loadConfig(env: EnvLike): Config {
 
   const allowedOrigins = deriveAllowedOrigins(port, env['ALLOWED_ORIGINS'])
 
+  // v0.6 Project Manager — discovery config
+  const projectRoots = parseProjectRoots(env['PROJECT_ROOTS'], homeDir)
+  const projectScanDepth = parseNonNegativeInt(
+    env['PROJECT_SCAN_DEPTH'],
+    'PROJECT_SCAN_DEPTH',
+    DEFAULT_PROJECT_SCAN_DEPTH,
+  )
+  const projectScanTtlMs = parseNonNegativeInt(
+    env['PROJECT_SCAN_TTL'],
+    'PROJECT_SCAN_TTL',
+    DEFAULT_PROJECT_SCAN_TTL_MS,
+  )
+  const projectDirtyCheck = parseBool(env['PROJECT_DIRTY_CHECK'], true)
+
   return Object.freeze({
     port,
     bindHost,
@@ -211,5 +248,9 @@ export function loadConfig(env: EnvLike): Config {
     previewBytes,
     useTmux,
     allowedOrigins,
+    projectRoots,
+    projectScanDepth,
+    projectScanTtlMs,
+    projectDirtyCheck,
   } satisfies Config)
 }