fix: maildir fetch errors

[andrinoff]

What?

Routes all per-account fetch sites in main.go through m.providers[acct.ID].

Why?

Fixes #1309

[floatpanebot]

Benchmark report — no significant change

Metrics worse: 0 · better: 0 (threshold: ±3%).

benchstat output

goos: linux
goarch: amd64
pkg: github.com/floatpane/matcha/backend
cpu: Intel(R) Xeon(R) Platinum 8370C CPU @ 2.80GHz
                           │    old.txt    │               new.txt               │
                           │    sec/op     │    sec/op      vs base              │
ParseSearchQuery_Simple-4    3.107µ ±  46%   2.721µ ± 157%       ~ (p=0.699 n=6)
ParseSearchQuery_Complex-4   7.867µ ±  44%   6.417µ ±  50%       ~ (p=0.818 n=6)
TokenizeSearchQuery-4        3.992µ ± 157%   4.534µ ±  41%       ~ (p=0.394 n=6)
geomean                      4.604µ          4.294µ         -6.73%

                           │  old.txt   │              new.txt               │
                           │    B/op    │    B/op     vs base                │
ParseSearchQuery_Simple-4    26.00 ± 0%   26.00 ± 0%       ~ (p=1.000 n=6) ¹
ParseSearchQuery_Complex-4   762.0 ± 0%   762.0 ± 0%       ~ (p=1.000 n=6) ¹
TokenizeSearchQuery-4        176.0 ± 0%   176.0 ± 0%       ~ (p=1.000 n=6) ¹
geomean                      151.6        151.6       +0.00%
¹ all samples are equal

                           │  old.txt   │              new.txt               │
                           │ allocs/op  │ allocs/op   vs base                │
ParseSearchQuery_Simple-4    2.000 ± 0%   2.000 ± 0%       ~ (p=1.000 n=6) ¹
ParseSearchQuery_Complex-4   23.00 ± 0%   23.00 ± 0%       ~ (p=1.000 n=6) ¹
TokenizeSearchQuery-4        9.000 ± 0%   9.000 ± 0%       ~ (p=1.000 n=6) ¹
geomean                      7.453        7.453       +0.00%
¹ all samples are equal

pkg: github.com/floatpane/matcha/tui
                    │   old.txt    │              new.txt               │
                    │    sec/op    │    sec/op     vs base              │
LogPanelView-4        147.1µ ± 23%   144.4µ ±  4%       ~ (p=0.310 n=6)
SearchOverlayView-4   165.2µ ±  6%   171.3µ ± 10%       ~ (p=0.180 n=6)
InboxConstruction-4   940.0µ ± 14%   913.0µ ±  7%       ~ (p=0.589 n=6)
geomean               283.7µ         282.6µ        -0.38%

                    │    old.txt    │                new.txt                │
                    │     B/op      │      B/op       vs base               │
LogPanelView-4        44.67Ki ± 51%   21.79Ki ± 105%        ~ (p=0.242 n=6)
SearchOverlayView-4   56.14Ki ± 41%   56.14Ki ±   0%        ~ (p=0.318 n=6)
InboxConstruction-4   874.2Ki ±  0%   874.2Ki ±   0%        ~ (p=0.900 n=6)
geomean               129.9Ki         102.3Ki         -21.29%

                    │   old.txt   │              new.txt              │
                    │  allocs/op  │  allocs/op   vs base              │
LogPanelView-4         714.0 ± 0%    712.0 ± 0%       ~ (p=0.242 n=6)
SearchOverlayView-4    926.0 ± 0%    926.0 ± 0%       ~ (p=0.273 n=6)
InboxConstruction-4   3.477k ± 0%   3.478k ± 0%       ~ (p=0.896 n=6)
geomean               1.320k        1.319k       -0.09%

_{auto-generated by benchmarks.yml}

[andrinoff]

/build

[floatpanebot]

Build complete (9ebb1b7)

Warning

This is an unreviewed PR build and has not been security audited. It may contain bugs, vulnerabilities, or malicious code. Do not use for daily use. Only use for testing purposes.

OS	Arch	Download
Linux	amd64	matcha_preview_linux_amd64.tar.gz
Linux	arm64	matcha_preview_linux_arm64.tar.gz
macOS	amd64	matcha_preview_darwin_amd64.tar.gz
macOS	arm64	matcha_preview_darwin_arm64.tar.gz
Windows	amd64	matcha_preview_windows_amd64.zip
Windows	arm64	matcha_preview_windows_arm64.zip

[andrinoff]

/build

[floatpanebot]

Build complete (9b10fbb)

Warning

This is an unreviewed PR build and has not been security audited. It may contain bugs, vulnerabilities, or malicious code. Do not use for daily use. Only use for testing purposes.

OS	Arch	Download
Linux	amd64	matcha_preview_linux_amd64.tar.gz
Linux	arm64	matcha_preview_linux_arm64.tar.gz
macOS	amd64	matcha_preview_darwin_amd64.tar.gz
macOS	arm64	matcha_preview_darwin_arm64.tar.gz
Windows	amd64	matcha_preview_windows_amd64.zip
Windows	arm64	matcha_preview_windows_arm64.zip

[FromSi]

Non-blocking follow-up: there are still a few legacy Trash/Archive helpers that call connect(account) before reaching the backend-aware fetch path, for example FetchTrashEmails, FetchTrashEmailBody, FetchTrashAttachment / FetchArchiveAttachment, and delete helpers in fetcher.go.

The main folder-based TUI flow now goes through the new maildir dispatch, so this PR fixes the reported maildir loading issue. But if a maildir account later reaches one of those mailbox-kind helpers directly, it can still fall back into the IMAP path and hit the same unsupported service_provider style error.