Add Learn tab; move quit to Safety; remove persistent MOB FAB

UI cleanup:
- Remove always-visible MOB FAB — Safety screen button is sufficient
- Remove floating quit button; move to bottom of Safety screen
- fragment_container is now clickable/focusable, blocking map touch-through
  for all overlays (trip reports, log, safety)
- Record Track FAB hidden while any overlay is shown, visible on map tab

New Learn tab (5th nav item):
- Migration guides for Navionics and Sea People (local markdown via DocFragment)
- ASA Course Catalog, ASA Online Learning, ColRegs, Sailing Flashcards
  (open in browser)
- Remove blanket assets/ .gitignore so markdown docs are tracked

https://claude.ai/code/session_01HXPjBsogsJVRwCiekDGkJX

3 files changed, 72 insertions, 9 deletions

diff --git a/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt b/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt
index 86dd531..996892e 100644
--- a/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt
+++ b/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt
@@ -54,9 +54,7 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
     private lateinit var bottomSheetBehavior: BottomSheetBehavior<View>
     private lateinit var fragmentContainer: FrameLayout
     private lateinit var fabRecordTrack: FloatingActionButton
-    private lateinit var fabMob: FloatingActionButton
     private lateinit var fabRecenter: MaterialButton
-    private lateinit var btnQuit: MaterialButton
     private lateinit var bottomSheet: CardView
     private lateinit var bottomNav: BottomNavigationView
     private lateinit var mapCrosshair: View
@@ -117,9 +115,7 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
     private fun initializeUI() {
         fragmentContainer = findViewById(R.id.fragment_container)
         fabRecordTrack = findViewById(R.id.fab_record_track)
-        fabMob = findViewById(R.id.fab_mob)
         fabRecenter = findViewById(R.id.fab_recenter)
-        btnQuit = findViewById(R.id.btn_quit)
         bottomSheet = findViewById(R.id.instrument_bottom_sheet)
         bottomNav = findViewById(R.id.bottom_navigation)
         mapCrosshair = findViewById(R.id.map_crosshair)
@@ -166,9 +162,7 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
             } else false
         }
 
-        fabMob.setOnClickListener { onActivateMob() }
         fabRecenter.setOnClickListener { mapHandler?.recenter() }
-        btnQuit.setOnClickListener { onQuitRequested() }
 
         lifecycleScope.launch {
             viewModel.isRecording.collect { recording ->
@@ -280,6 +274,12 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
                     bottomSheetBehavior.state = BottomSheetBehavior.STATE_HIDDEN
                     true
                 }
+                R.id.nav_learn -> {
+                    showOverlay(org.terst.nav.ui.learn.LearnFragment())
+                    bottomSheetBehavior.isHideable = true
+                    bottomSheetBehavior.state = BottomSheetBehavior.STATE_HIDDEN
+                    true
+                }
                 else -> false
             }
         }
@@ -287,6 +287,7 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
 
     private fun showOverlay(fragment: androidx.fragment.app.Fragment) {
         fragmentContainer.visibility = View.VISIBLE
+        fabRecordTrack.visibility = View.GONE
         supportFragmentManager.beginTransaction()
             .replace(R.id.fragment_container, fragment)
             .commit()
@@ -294,9 +295,10 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
 
     private fun hideOverlays() {
         fragmentContainer.visibility = View.GONE
+        fabRecordTrack.visibility = View.VISIBLE
     }
 
-    private fun onQuitRequested() {
+    override fun onQuitRequested() {
         if (viewModel.isRecording.value) {
             androidx.appcompat.app.AlertDialog.Builder(this)
                 .setMessage("Recording in progress. Quit and discard the current track?")
@@ -405,9 +407,9 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
                     mapCrosshair.visibility = if (following) View.GONE else View.VISIBLE
                     if (following) {
                         fadeOut(fabRecenter, gone = true)
-                        fadeIn(bottomNav, fabMob, fabRecordTrack)
+                        fadeIn(bottomNav, fabRecordTrack)
                     } else {
-                        fadeOut(bottomNav, fabMob, fabRecordTrack, gone = true)
+                        fadeOut(bottomNav, fabRecordTrack, gone = true)
                         fadeIn(fabRecenter)
                     }
                 }
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/ui/learn/LearnFragment.kt b/android-app/app/src/main/kotlin/org/terst/nav/ui/learn/LearnFragment.kt
new file mode 100644
index 0000000..8440edb
--- /dev/null
+++ b/android-app/app/src/main/kotlin/org/terst/nav/ui/learn/LearnFragment.kt
@@ -0,0 +1,56 @@
+package org.terst.nav.ui.learn
+
+import android.content.Intent
+import android.net.Uri
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import androidx.fragment.app.Fragment
+import com.google.android.material.card.MaterialCardView
+import org.terst.nav.R
+import org.terst.nav.ui.doc.DocFragment
+
+class LearnFragment : Fragment() {
+
+    override fun onCreateView(
+        inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?
+    ): View? = inflater.inflate(R.layout.fragment_learn, container, false)
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        super.onViewCreated(view, savedInstanceState)
+
+        // Migration guides — open local markdown docs
+        view.findViewById<MaterialCardView>(R.id.card_migrate_navionics).setOnClickListener {
+            openDoc("docs/migrate_navionics.md")
+        }
+        view.findViewById<MaterialCardView>(R.id.card_migrate_seapeople).setOnClickListener {
+            openDoc("docs/migrate_sea_people.md")
+        }
+
+        // ASA / external links — open in browser
+        view.findViewById<MaterialCardView>(R.id.card_asa_courses).setOnClickListener {
+            openUrl("https://www.asa.com/courses/")
+        }
+        view.findViewById<MaterialCardView>(R.id.card_asa_online).setOnClickListener {
+            openUrl("https://www.asa.com/online-courses/")
+        }
+        view.findViewById<MaterialCardView>(R.id.card_colregs).setOnClickListener {
+            openUrl("https://www.navcen.uscg.gov/international-regulations-for-preventing-collisions-at-sea")
+        }
+        view.findViewById<MaterialCardView>(R.id.card_flashcards).setOnClickListener {
+            openUrl("https://quizlet.com/subject/sailing/")
+        }
+    }
+
+    private fun openDoc(path: String) {
+        parentFragmentManager.beginTransaction()
+            .replace(R.id.fragment_container, DocFragment.newInstance(path))
+            .addToBackStack(null)
+            .commit()
+    }
+
+    private fun openUrl(url: String) {
+        startActivity(Intent(Intent.ACTION_VIEW, Uri.parse(url)))
+    }
+}
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/ui/safety/SafetyFragment.kt b/android-app/app/src/main/kotlin/org/terst/nav/ui/safety/SafetyFragment.kt
index 4bc0c7a..6dd7411 100644
--- a/android-app/app/src/main/kotlin/org/terst/nav/ui/safety/SafetyFragment.kt
+++ b/android-app/app/src/main/kotlin/org/terst/nav/ui/safety/SafetyFragment.kt
@@ -15,6 +15,7 @@ class SafetyFragment : Fragment() {
     interface SafetyListener {
         fun onActivateMob()
         fun onConfigureAnchor()
+        fun onQuitRequested()
     }
 
     private var listener: SafetyListener? = null
@@ -55,6 +56,10 @@ class SafetyFragment : Fragment() {
                 .addToBackStack(null)
                 .commit()
         }
+
+        view.findViewById<MaterialButton>(R.id.button_quit).setOnClickListener {
+            listener?.onQuitRequested()
+        }
     }
 
     fun updateAnchorStatus(statusText: String) {