fix: describe merge order as FIFO, not 'bottom-first'

A 'stack' evokes LIFO (pop the top first), so 'bottom-first' reads as
contradictory. The order is unchanged — the first/base PR merges first — but the
PR-body caption and README now frame it as FIFO (#1 first) to avoid confusion.

Author: freshtonic

README.md

@@ -106,10 +106,11 @@ git stack submit               # refresh the PRs
 
 ### Landing a stack
 
-PRs merge **bottom-first**. After the bottom PR lands, run `git stack sync` — it
-detects the merged PR, reparents the branches above onto trunk, and rebases
+PRs merge in **FIFO order** — the oldest PR (`#1`, at the base of the stack)
+merges first, then the next, and so on. After a PR lands, run `git stack sync` —
+it detects the merged PR, reparents the branches above onto trunk, and rebases
 them; then `git stack submit` retargets their PR bases and refreshes the stack
-list. Each PR body shows live approval/merge-state emojis (✅/🔴/⏳ while open,
+list. Each PR body shows live approval/merge-state emojis (✅/♻️/⏳ while open,
 🟣/⚫ once merged/closed) as of the last submit.
 
 ### Editing a branch in the middle of a stack
@@ -160,11 +161,11 @@ top, followed by that branch's `describe` text under a divider:
 ```markdown
 ### 📚 Stacked PR · 2 of 3
 
-Merge in order, bottom to top:
+Part of a stack. The PRs merge in FIFO order — the numbered order below, #1 first.
 
-1. [#10 `api`](…/pull/10) → `main`
-2. **[#11 `service`](…/pull/11) → `api`**  👈 **this PR**
-3. [#12 `ui`](…/pull/12) → `service`
+1. 🟣 [#10 `api`](…/pull/10) → `main`
+2. ♻️🟢 **[#11 `service`](…/pull/11) → `api`**  👈 **this PR**
+3. ⏳🟢 [#12 `ui`](…/pull/12) → `service`
 
 ---
 

src/render.rs

@@ -71,9 +71,10 @@ pub fn nav_block(line: &[Entry], current: &str, trunk: &str) -> String {
             total
         ),
         String::new(),
-        "Part of a stack (listed bottom → top). PRs merge bottom-first; merging one \
-         supersedes the PRs above it until the author runs `git stack sync` (rebases the \
-         rest onto the merged base) and `git stack submit` (retargets their PRs)."
+        "Part of a stack. The PRs merge in FIFO order — the numbered order below, #1 \
+         first. Merging one supersedes the PRs after it until the author runs \
+         `git stack sync` (rebases the rest onto the merged base) and `git stack submit` \
+         (retargets their PRs)."
             .to_string(),
         String::new(),
     ];
@@ -260,9 +261,10 @@ mod tests {
         assert!(nav.contains("3. ⏳🟢 [#12 `ui`]"), "{nav}");
         assert!(nav.contains("👈 **this PR**"));
         assert!(nav.contains("2 of 3"));
+        assert!(nav.contains("FIFO"), "merge order described as FIFO");
         assert!(
-            !nav.contains("Merge in order"),
-            "old misleading caption removed"
+            !nav.contains("bottom-first"),
+            "confusing bottom-first wording removed"
         );
     }
 }