Keep point and scroll steady in the eca-workspaces dashboard

[agzam]

TL;DR

The eca-workspaces dashboard stays where you left it while chats run. Before, the once-a-second refresh scrolled the view and could throw point to the top, which made the buffer impossible to navigate.

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Problem

eca-workspaces--render erases the buffer and re-inserts every row, so it has to put the view back afterwards. It restored point by row entity and missed two things:

• erase-buffer deletes all text, so every marker into the buffer collapses to position 1, window-start included. Nothing restored it, so after the re-insert each window started at line 1 with point further down, and redisplay recentered point. A window shorter than the content, which the bottom side window usually is, scrolled on every tick.
• Only workspace and chat rows carry the eca-workspaces-session-id property. Point on the footer or the blank line above it had no entity, so eca-workspaces--restore-point fell back to point-min, once a second.

Both paths fire continuously while a chat streams: the 1s elapsed-time ticker and the debounced refresh on chat status changes.

Change

• eca-workspaces--window-state also records (line-number-at-pos (window-start window)), and the render restores it with set-window-start ... t, after setting the window point. NOFORCE means redisplay ignores a start that would push point off screen, e.g. when rows above it disappeared.
• eca-workspaces--restore-point gives way to eca-workspaces--point-state and eca-workspaces--point-position. The state is (ENTITY COLUMN LINE): a line without an entity is found again by its line number, so point on the footer survives; a row whose entity is gone still falls back to buffer start.

Testing

Two new specs: point on the footer line survives a render, and a window keeps both its start line and its point row. Both fail on master with exactly the reported symptom (window start line 1 instead of 3, point line 1 instead of 4). Full suite: 732 specs, 0 failed. checkdoc clean.

Also verified live: three consecutive eca-workspaces-refresh calls in a real window keep the window start line, the point row, and point on the footer.

[agzam]

@ericdallo CI is red here, but not from this change. The four failing jobs (ubuntu and macos on Emacs 28.1 and 28.2) pass Byte-compile, both lints and Run tests. They fail in Package, on eask install:

- [1/1] Installing package-build (20260924.1014)... Package ‘emacs-29.1’ is unavailable

MELPA published package-build today with an Emacs 29.1 requirement, so eask cannot install it on Emacs 28.

[ericdallo]

I fixed, can you rebase master pls