feat(projects): fix cancelling, track shared projects, flag unreachable pipelines

[camielvs]

Four things, all downstream of projects becoming shareable by URL.

1. The New Project dialog could not be cancelled

Not a veto — a layout shift. The Name field is autoFocused, so pressing the
mouse on Cancel blurred it, onBlur set nameTouched, and a ~50px <Alert>
mounted between mousedown and mouseup. DialogContent is
top-[50%] translate-y-[-50%], so the panel grew in both directions and the
footer slid out from under the cursor. A click needs mousedown and mouseup on
the same element, so none was ever produced. RenameProjectDialog was a
verbatim copy of the same pattern.

The complaint now waits for a press of Create — which is also what asks for it,
so Create stops being disabled while the name is empty (a disabled button fires
no submit, and the message would be unreachable).

Measured in a real browser, one Cancel click:

	dialog still open afterwards
before	true
after	false

2. Resolving a local pipeline by name was a wrong-pipeline hazard

A pointer recorded a registry id, but resolution fell back to the pipeline's
name when the id did not resolve. Within one browser that is merely
imprecise. Across browsers it is wrong: a project is shared, the pointer lands
in a browser holding an unrelated pipeline of the same name, and the fallback
claims it.

• where the resource recorded a name/ identity, that opened the wrong
  pipeline, silently;
• where it recorded an id/ identity, the row read as available and then failed
  on click.

A recorded id is now the whole answer: an id that does not resolve means the
pipeline is not here. A pointer that recorded no id has only ever had its name,
so it is still resolved by name — but trusted only in the browser that wrote it,
which is resource.createdBy. Unknown authorship stays trusted, so single-user
backends are unaffected.

Two existing tests pinned the old fallback; both are replaced by tests asserting
the new rule, and the cross-browser collision is now covered directly.

3. Pipelines that cannot travel with the project listing them

Rows now read "Pipeline — not in this browser" and grey out, matching the
"Backend pipeline — not supported yet" row directly beside them. Remove still
works, because unopenable is not unremovable. Previously such a row opened a tab
that collapsed into a red error icon and filed a Bugsnag report for an entirely
expected situation.

Only a definite negative greys a row out — while the lookup runs, rows are left
alone rather than flickering.

4. Pinning, and a way out of Tangent

/projects only lists what the caller created, so a shared project was gone with
the link.

• Pin a project from the card's own menu, or from either project header.
• Pinning reorders rather than copying: a pinned project sorts to the front
  of the one grid and carries a pin in place of its folder icon. It stays an
  ordinary card — ⋮ menu, resource counts and dates all intact — and the list
  leaves out whatever is pinned, so each project is on screen exactly once. A
  project that arrived by a shared link was never in the list to begin with, and
  simply joins the front. "Showing N of M" follows.
• The heading is now Projects rather than My Projects, since a pinned
  project may be someone else's.
• Pins are local — the backend has no notion of who a project was shared with —
  so usePinnedProjects is deliberately the single seam to replace if it ever
  grows a server side. They ride on the existing favourites store, so a pinned
  project also appears under Favourites.
• Visits are recorded too, but they feed the existing Recently viewed list
  rather than this page.
• Tangent gains a back to projects link in the project header. The only way
  out was the logo, which leaves Tangent altogether rather than going up one
  level.

5. A deleted project that would not go away

Deleting a project left its links behind, and following one opened its Tangent
page with everything apparently intact.

• The delete invalidated the detail query rather than removing it. An
  invalidated query keeps its data, so the next page to mount it was served the
  cached project in full and only then refetched its way to an error. It now
  removes it.
• Recently Viewed and Favourites are local records the backend cannot prune, so
  the delete prunes them. Recent lists also update in the tab that wrote them —
  storage events only ever reached the other tabs.
• The Tangent page never asked whether the project existed. A deleted one
  resolves no workspace to take a Tangent url from, so it sat on
  "Loading project…" indefinitely; it now says the project is gone and offers
  the way back.
• Following a dead link no longer re-records it: a deleted project keeps its
  last-known name in the cache, which was enough to put it straight back on the
  list.

Verified against the local backend: created a project, opened it, deleted it
from its card, and confirmed it is absent from Recently Viewed and that its url
reads "Project not found" rather than spinning.

Testing

Full suite green — 313 files, 3178 passed.

Verified in the browser against the local backend: one-click cancel; the card
menu reading Pin project / Details / Share project / Delete project; a pinned
project moving to the head of the grid, appearing once, keeping its menu,
counts and dates, and carrying the pin marker; a genuinely absent local pipeline
greyed with its message; and the back link landing on /projects.

jsdom cannot catch item 1 at all — it has no layout, so userEvent.click
dispatches at the element reference wherever it has "moved".

🤖 Generated with Claude Code

[github-actions]

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A preview build has been created at: 09-22-feat_projects_that_can_be_shared_and_cancelled/e5a678c

[camielvs]

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• fix(runs): say why the backend refused a run instead of that it did #2794 : 2 dependent PRs (#2796 , #2798 )
• feat(tangent): brief the agent on naming, and on the project its runs belong to #2792
• feat(projects): fix cancelling, track shared projects, flag unreachable pipelines #2790 👈 (View in Graphite)
• feat(tangent): keep an agent's edits in frame on the canvas #2789
• feat(tangent): bring Tangent onto the dashboard #2787
• feat(tangent): show a project's runs on the tangent page #2786
• fix(projects): show an agent's run on the project it belongs to #2785
• fix(agent): submit a spec that came from the editor's store #2784
• chore: increase max turns in remote agent #2779
• fix(tangent): stop the tab strips scrolling up and down #2777
• feat(projects): make the agents' instructions a project document #2776
• feat(tangent): list the pipelines the backend holds #2775
• feat(projects): show a project's documents on both pages #2774
• fix(tangent): project window parity — share, new-session links, agent-created pipelines, and a folded-away project window #2773
• refactor(projects): describe a project's resources one way #2765
• feat(projects): delete and share a project from either page #2764
• feat: open a new project ready to work in #2763
• feat: let the project page and Tangent reach each other #2762
• fix: keep a long project name inside the tile it belongs to #2761
• feat: say so when Tangent cannot be reached #2760
• feat: open a project where the work happens #2759
• feat: run a pipeline inside a project #2754
• feat: add pipelines held in this browser to a project #2745
• feat: project page #2738
• feat: create a project from a tile in the grid #2735 : 2 other dependent PRs (#2736 , #2737 )
• feat: projects dashboard #2734
• chore: tangent - annotate runs submission to projectid #2758
• fix: tangent - proper debug sequence system prompt #2757
• fix: tangent - quick run button from mini content window #2744
• fix: tangent - remote agent send delta immediately #2743
• fix: tangent - mint proper authorization with tangent #2742
• feat: tangent - debug in tangent sequence #2741
• chore: add autolayout tool #2740
• feat: tangent - resource management via document entity #2733
• feat: tangent - interactive chips in tangent chat #2732
• chore: save id stack to replay ids on reloads #2731
• refactor: tangent - migrate tangetproectcontext onto mobx #2730
• feat: tangent - keep track of open tabs while switching sessions inside project #2729
• feat: tangent - remote agent for runview and editor #2728
• refactor: tangent - structured workarea target #2727
• feat: tangent - embedded pipeline run view #2726
• feat: tangent - embedded pipeline editor #2725
• feat: tangent - dynamic workarea remote tools #2724
• feat: tangent - resources management in project view #2723
• feat: tangent project view page #2722
• feat: workspaces and projects service #2720
• chore: api client for workspaces and projects #2719
• master

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