Declare provider settings, and give the context figure a denominator

Two things a session could not say, and one it was saying wrongly.

**Every provider setting is reachable.** `-np 1`, the MTP draft depth, the
tool set, the sampling parameters -- most were hardcoded to what measured
best on this machine, which is right as a default and wrong as a constant:
the next machine has a different GPU and a different core count, and
nobody running this app can edit the source. `DriverKind::params` now
declares what a provider takes -- key, label, shape, what blank means, and
whether a change waits for a restart -- and the phone renders whatever
arrives, on the spawn form and in the session settings dialog. Adding a
setting to a driver is one entry in that table and no app change.
`POST /sessions/{id}/params` takes the whole map, so an absent key is the
instruction to unset; the sampling half applies at once and the session is
told in words which of the rest are waiting for a restart.

`tools` is one of them, because it is the biggest lever on a tight
context: the seven built-in definitions are ~1,300 tokens of every prompt
(2,191 against 887 with none). `"none"` omits the flag rather than passing
it on, since `--tools none` is `unknown tool "none"` and a server that
exits.

**The context figure has a denominator.** `Event::ContextWindow` carries
it, read from `llama-server`'s `/props` once the model is up -- the
measurement rather than the request, since a session that named no context
size gets the model's own. Neither coding CLI states its window, so those
keep the bare figure: "2,042" and "2,042 / 8,192" are deliberately
different-looking, and a missing ceiling is never drawn as a proportion of
an assumed one.

**And the numerator was wrong**, by the length of the last reply: it was
the prompt alone, so a five-word answer reported 2,042 against a slot
holding 2,355. It is the turn's total now, which matches `llama-server`'s
own `n_tokens` to within a token.

Two defects the review found, both of which would have shipped: changing
settings on a *stopped* session reported "no process running, so it can't
take new settings", when a stopped session is exactly when you would set
them for the next start; and `GET /tools` answers **403** rather than an
empty list on a server started without `--tools`, so reading it as a
failure made the no-tools session one that never started.

Verified against real models: settings spawned and changed live, the
restart note, a session with two tools and one with none, and the counter
checked against the server's own slot occupancy each time.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

app/androidApp/src/main/kotlin/com/example/aiapp/ProviderParams.kt

@@ -0,0 +1,117 @@
+package com.example.aiapp
+
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.text.KeyboardOptions
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.OutlinedTextField
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.input.KeyboardType
+import androidx.compose.ui.unit.dp
+
+/**
+ * The controls for whatever settings a provider says it takes.
+ *
+ * One composable for both screens that offer them — the spawn form and the session settings dialog
+ * — and for every provider, because the server declares the list (see `DriverKind::params`) rather
+ * than this file knowing it. A driver that grows a setting gets a control here with no change to
+ * the app, which is the whole point: the values that suit one machine ship as defaults, and every
+ * one of them stays reachable from a phone.
+ *
+ * [values] is the whole map and [onChange] hands back the whole map. A key absent from it means the
+ * setting is unset, which is what every [ParamSpec.unset] describes — so clearing a field and never
+ * touching it are deliberately the same state.
+ */
+@Composable
+fun ProviderParamFields(
+    specs: List<ParamSpec>,
+    values: Map<String, String>,
+    onChange: (Map<String, String>) -> Unit,
+    /**
+     * Whether to say which settings wait for a restart. False on a spawn form, where nothing is
+     * running yet and every setting is about to be read — saying it there would be a warning about
+     * a state the reader cannot be in.
+     */
+    warnAboutRestart: Boolean,
+    modifier: Modifier = Modifier,
+) {
+    if (specs.isEmpty()) return
+    Column(modifier.fillMaxWidth()) {
+        specs.forEach { spec ->
+            val set = { value: String ->
+                onChange(
+                    // Blank clears rather than storing an empty string: the server reads an absent
+                    // key as "use the default", and an empty one would be a value it then failed
+                    // to parse.
+                    if (value.isBlank()) values - spec.key else values + (spec.key to value)
+                )
+            }
+            when (spec.kind) {
+                "choice" -> {
+                    // The first option is what unset means, so selecting it clears the key — see
+                    // `ParamKind::Choice`. Without that the picker could show a default it could
+                    // not return to.
+                    val default = spec.options.firstOrNull().orEmpty()
+                    ChipGroup(
+                        label = spec.label + restartSuffix(spec, warnAboutRestart),
+                        options = spec.options,
+                        selected = values[spec.key] ?: default,
+                        onSelect = { chosen -> set(if (chosen == default) "" else chosen) },
+                    )
+                }
+                else ->
+                    OutlinedTextField(
+                        value = values[spec.key].orEmpty(),
+                        onValueChange = set,
+                        label = { Text(spec.label + restartSuffix(spec, warnAboutRestart)) },
+                        placeholder = { Text(spec.unset) },
+                        singleLine = true,
+                        keyboardOptions = KeyboardOptions(keyboardType = keyboardFor(spec.kind)),
+                        modifier = Modifier.fillMaxWidth(),
+                    )
+            }
+            Spacer(Modifier.height(16.dp))
+        }
+        if (warnAboutRestart && specs.any { it.restart }) {
+            Text(
+                "A setting marked “on restart” is saved now and read when this session's process " +
+                    "next starts.",
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+        }
+    }
+}
+
+/**
+ * Marks a control whose value will not take effect yet.
+ *
+ * On the label rather than beside it, because the reader decides whether to change the thing before
+ * they touch it — a note underneath is read after the decision.
+ */
+private fun restartSuffix(spec: ParamSpec, warn: Boolean): String =
+    if (warn && spec.restart) " (on restart)" else ""
+
+/**
+ * The keyboard for a value's shape. A number field that opens the letter keyboard is one every
+ * entry is made harder by, and these are nearly all numbers.
+ */
+private fun keyboardFor(kind: String): KeyboardType =
+    when (kind) {
+        "integer" -> KeyboardType.Number
+        "decimal" -> KeyboardType.Decimal
+        else -> KeyboardType.Text
+    }
+
+/**
+ * How long typing has to stop before edited settings are sent.
+ *
+ * Long enough that a number is one request rather than one per digit, short enough that closing the
+ * dialog straight after typing still saves — the save runs on the screen behind it, which outlives
+ * the dialog, so this delay is not a window the value can be lost in.
+ */
+const val PARAM_SAVE_DELAY_MS = 700L